SherbyNet - /page/wikibook/entry.mu

Micron Document

<!DOCTYPE html>

</head>

</h1>

</header>

/* start https://en.wikipedia.org/ */

.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}

/* end https://en.wikipedia.org/ */

</style><div role="note" class="hatnote navigation-not-searchable">"404 Not Found" redirects here. For the TV episode, see <a href="404_Not_Found_(Mr._Robot)" title="404 Not Found (Mr. Robot)">404 Not Found (<i>Mr. Robot</i>)</a>.</div>

</p>

/* start https://en.wikipedia.org/ */

.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · ";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output .hlist dt:last-child::after,.mw-parser-output .hlist li:last-child::after{content:none}.mw-parser-output .hlist dd dd:first-child::before,.mw-parser-output .hlist dd dt:first-child::before,.mw-parser-output .hlist dd li:first-child::before,.mw-parser-output .hlist dt dd:first-child::before,.mw-parser-output .hlist dt dt:first-child::before,.mw-parser-output .hlist dt li:first-child::before,.mw-parser-output .hlist li dd:first-child::before,.mw-parser-output .hlist li dt:first-child::before,.mw-parser-output .hlist li li:first-child::before{content:" (";font-weight:normal}.mw-parser-output .hlist dd dd:last-child::after,.mw-parser-output .hlist dd dt:last-child::after,.mw-parser-output .hlist dd li:last-child::after,.mw-parser-output .hlist dt dd:last-child::after,.mw-parser-output .hlist dt dt:last-child::after,.mw-parser-output .hlist dt li:last-child::after,.mw-parser-output .hlist li dd:last-child::after,.mw-parser-output .hlist li dt:last-child::after,.mw-parser-output .hlist li li:last-child::after{content:")";font-weight:normal}.mw-parser-output .hlist ol{counter-reset:listitem}.mw-parser-output .hlist ol>li{counter-increment:listitem}.mw-parser-output .hlist ol>li::before{content:" "counter(listitem)"\a0 "}.mw-parser-output .hlist dd ol>li:first-child::before,.mw-parser-output .hlist dt ol>li:first-child::before,.mw-parser-output .hlist li ol>li:first-child::before{content:" ("counter(listitem)"\a0 "}

/* end https://en.wikipedia.org/ */

</style><style data-mw-deduplicate="TemplateStyles:r1246091330">

/* start https://en.wikipedia.org/ */

.mw-parser-output .sidebar{width:22em;float:right;clear:right;margin:0.5em 0 1em 1em;background:var(--background-color-neutral-subtle,#f8f9fa);border:1px solid var(--border-color-base,#a2a9b1);padding:0.2em;text-align:center;line-height:1.4em;font-size:88%;border-collapse:collapse;display:table}body.skin-minerva .mw-parser-output .sidebar{display:table!important;float:right!important;margin:0.5em 0 1em 1em!important}.mw-parser-output .sidebar-subgroup{width:100%;margin:0;border-spacing:0}.mw-parser-output .sidebar-left{float:left;clear:left;margin:0.5em 1em 1em 0}.mw-parser-output .sidebar-none{float:none;clear:both;margin:0.5em 1em 1em 0}.mw-parser-output .sidebar-outer-title{padding:0 0.4em 0.2em;font-size:125%;line-height:1.2em;font-weight:bold}.mw-parser-output .sidebar-top-image{padding:0.4em}.mw-parser-output .sidebar-top-caption,.mw-parser-output .sidebar-pretitle-with-top-image,.mw-parser-output .sidebar-caption{padding:0.2em 0.4em 0;line-height:1.2em}.mw-parser-output .sidebar-pretitle{padding:0.4em 0.4em 0;line-height:1.2em}.mw-parser-output .sidebar-title,.mw-parser-output .sidebar-title-with-pretitle{padding:0.2em 0.8em;font-size:145%;line-height:1.2em}.mw-parser-output .sidebar-title-with-pretitle{padding:0.1em 0.4em}.mw-parser-output .sidebar-image{padding:0.2em 0.4em 0.4em}.mw-parser-output .sidebar-heading{padding:0.1em 0.4em}.mw-parser-output .sidebar-content{padding:0 0.5em 0.4em}.mw-parser-output .sidebar-content-with-subgroup{padding:0.1em 0.4em 0.2em}.mw-parser-output .sidebar-above,.mw-parser-output .sidebar-below{padding:0.3em 0.8em;font-weight:bold}.mw-parser-output .sidebar-collapse .sidebar-above,.mw-parser-output .sidebar-collapse .sidebar-below{border-top:1px solid #aaa;border-bottom:1px solid #aaa}.mw-parser-output .sidebar-navbar{text-align:right;font-size:115%;padding:0 0.4em 0.4em}.mw-parser-output .sidebar-list-title{padding:0 0.4em;text-align:left;font-weight:bold;line-height:1.6em;font-size:105%}.mw-parser-output .sidebar-list-title-c{padding:0 0.4em;text-align:center;margin:0 3.3em}@media(max-width:640px){body.mediawiki .mw-parser-output .sidebar{width:100%!important;clear:both;float:none!important;margin-left:0!important;margin-right:0!important}}body.skin--responsive .mw-parser-output .sidebar a>img{max-width:none!important}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-night .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-list-title,html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle{background:transparent!important}html.skin-theme-clientpref-os .mw-parser-output .sidebar:not(.notheme) .sidebar-title-with-pretitle a{color:var(--color-progressive)!important}}@media print{body.ns-0 .mw-parser-output .sidebar{display:none!important}}

/* end https://en.wikipedia.org/ */

</style><table class="sidebar nomobile nowraplinks hlist"><tbody><tr><th class="sidebar-title"><a href="HTTP" title="HTTP">HTTP</a></th></tr><tr><td class="sidebar-image"><span typeof="mw:File"></span></td></tr><tr><td class="sidebar-content">

<ul><li><a href="HTTP_persistent_connection" title="HTTP persistent connection">Persistence</a></li>

<li><a href="HTTP_compression" title="HTTP compression">Compression</a></li>

<li><a href="HTTPS" title="HTTPS">HTTPS</a></li>

</tr><tr><th class="sidebar-heading">

<a href="HTTP#Request_methods" title="HTTP">Request methods</a></th></tr><tr><td class="sidebar-content">

<ul><li><a href="HTTP#Request_methods" title="HTTP">OPTIONS</a></li>

<li><a href="HTTP#Request_methods" title="HTTP">DELETE</a></li>

<li><a href="HTTP#Request_methods" title="HTTP">TRACE</a></li>

<li><a href="HTTP#Request_methods" title="HTTP">CONNECT</a></li>

<li><a href="PATCH_(HTTP)" title="PATCH (HTTP)">PATCH</a></li></ul></td>

</tr><tr><th class="sidebar-heading">

<a href="List_of_HTTP_header_fields" title="List of HTTP header fields">Header fields</a></th></tr><tr><td class="sidebar-content">

<ul><li><a href="HTTP_cookie" title="HTTP cookie">Cookie</a></li>

<li><a href="HTTP_location" title="HTTP location">Location</a></li>

<li><a href="HTTP_referer" title="HTTP referer">HTTP referer</a></li>

<li><a href="X-Forwarded-For" title="X-Forwarded-For">X-Forwarded-For</a></li></ul></td>

</tr><tr><th class="sidebar-heading">

<a href="List_of_HTTP_status_codes" title="List of HTTP status codes">Response status codes</a></th></tr><tr><td class="sidebar-content">

<ul><li><a href="HTTP_301" title="HTTP 301">301 Moved Permanently</a></li>

<li><a href="HTTP_302" title="HTTP 302">302 Found</a></li>

<li><a href="HTTP_303" title="HTTP 303">303 See Other</a></li>

<li><a href="HTTP_403" title="HTTP 403">403 Forbidden</a></li>

<li><a href="HTTP_451" title="HTTP 451">451 Unavailable for Legal Reasons</a></li></ul></td>

</tr><tr><th class="sidebar-heading">

Security access control methods</th></tr><tr><td class="sidebar-content">

<ul><li><a href="Basic_access_authentication" title="Basic access authentication">Basic access authentication</a></li>

<li><a href="Digest_access_authentication" title="Digest access authentication">Digest access authentication</a></li></ul></td>

</tr><tr><th class="sidebar-heading">

Security vulnerabilities</th></tr><tr><td class="sidebar-content">

<ul><li><a href="HTTP_header_injection" title="HTTP header injection">HTTP header injection</a></li>

<li><a href="HTTP_request_smuggling" title="HTTP request smuggling">HTTP request smuggling</a></li>

<li><a href="HTTP_response_splitting" title="HTTP response splitting">HTTP response splitting</a></li>

<li><a href="HTTP_parameter_pollution" title="HTTP parameter pollution">HTTP parameter pollution</a></li></ul></td>

</tr><tr><td class="sidebar-navbar"><style data-mw-deduplicate="TemplateStyles:r1239400231">

/* start https://en.wikipedia.org/ */

.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}

/* end https://en.wikipedia.org/ */

</style></td></tr></tbody></table>

<p>

In <a href="Data_communication" title="Data communication">computer network communications</a>, the <b>HTTP 404</b>, <b>404 not found</b>, <b>404</b>, <b>404 error</b>, <b>page not found</b>, or <b>file not found</b> <a href="Error_message" title="Error message">error message</a> is a <a href="Hypertext_transfer_protocol" class="mw-redirect" title="Hypertext transfer protocol">hypertext transfer protocol</a> (HTTP) <a href="List_of_HTTP_status_codes" title="List of HTTP status codes">standard response code</a>, to indicate that the <a href="Web_browser" title="Web browser">browser</a> was able to communicate with a given <a href="Server_(computing)" title="Server (computing)">server</a>, but the server could not find what was requested. The error may also be used when a server does not wish to disclose whether it has the requested information.<sup id="cite_ref-section-654_1-0" class="reference"><a href="#cite_note-section-654-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

</p><p>The website hosting server will typically generate a "404 Not Found" web page when a user attempts to follow a <a href="Link_rot" title="Link rot">broken or dead link</a>; hence the 404 error is one of the most recognizable errors encountered on the <a href="World_Wide_Web" title="World Wide Web">World Wide Web</a>.

</p>

<div class="mw-heading mw-heading2"><h2 id="Overview">Overview</h2></div>

<p>When communicating via HTTP, a server is required to respond to a request, such as a <a href="Web_browser" title="Web browser">web browser</a> request for a <a href="Web_page" title="Web page">web page</a>, with a numeric response code and an optional, mandatory, or disallowed (based upon the status code) message. In code 404, the first digit indicates a client error, such as a mistyped <a href="Uniform_Resource_Locator" class="mw-redirect" title="Uniform Resource Locator">Uniform Resource Locator</a> (URL). The following two digits indicate the specific error encountered. HTTP's use of three-digit codes is similar to the use of such codes in earlier protocols such as <a href="File_Transfer_Protocol" title="File Transfer Protocol">FTP</a> and <a href="Network_News_Transfer_Protocol" title="Network News Transfer Protocol">NNTP</a>. At the HTTP level, a 404 response code is followed by a human-readable "reason phrase". The HTTP specification suggests the phrase "Not Found"<sup id="cite_ref-section-654_1-1" class="reference"><a href="#cite_note-section-654-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> and many web servers by default issue an HTML page that includes both the 404 code and the "Not Found" phrase.

</p><p>A 404 error is often returned when pages have been moved or deleted. In the first case, it is better to employ <a href="URL_mapping" class="mw-redirect" title="URL mapping">URL mapping</a> or <a href="URL_redirection" title="URL redirection">URL redirection</a> by returning a 301 Moved Permanently response, which can be configured in most server configuration files, or through <a href="URL_rewriting" class="mw-redirect" title="URL rewriting">URL rewriting</a>; in the second case, a 410 Gone should be returned. Because these two options require special server configuration, most websites do not make use of them.

</p><p>404 errors should not be confused with <a href="Domain_Name_System" title="Domain Name System">DNS</a> errors, which appear when the given URL refers to a server name that does not exist. A 404 error indicates that the server itself was found, but that the server was not able to retrieve the requested page.

</p>

<div class="mw-heading mw-heading2"><h2 id="Soft_404_errors">Soft 404 errors</h2></div>

<p>

</p><p>Some websites report a "not found" error by returning a standard web page with a "200 OK" response code, falsely reporting that the page loaded properly; this is known as a <i>soft 404</i>. The term "soft 404" was introduced in 2004 by Ziv Bar-Yossef <i>et al</i>.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>Soft 404s are problematic for automated methods of discovering whether a link is broken. Some search engines, like <a href="Yahoo" title="Yahoo">Yahoo</a> and <a href="Google" title="Google">Google</a>, use automated processes to detect soft 404s.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Soft 404s can occur as a result of configuration errors when using certain HTTP server software, for example with the <a href="Apache_HTTP_Server" title="Apache HTTP Server">Apache</a> software, when an Error Document 404 (specified in a <a href=".htaccess" title=".htaccess">.htaccess</a> file) is specified as an absolute path (e.g. http://example.com/error.html) rather than a relative path (/error.html).<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> This can also be done on purpose to force some browsers (like <a href="Internet_Explorer" title="Internet Explorer">Internet Explorer</a>) to display a customized 404 error message rather than replacing what is served with a browser-specific "friendly" error message (in Internet Explorer, this behavior is triggered when a 404 is served and the received HTML is shorter than a certain length, and can be manually disabled by the user).

</p><p>There are also "soft 3XX" errors where content is returned with a status 200 but comes from a redirected page, such as when missing pages are redirected to the domain root/home page.

</p>

<div class="mw-heading mw-heading3"><h3 id="Proxy_servers">Proxy servers</h3></div>

<p>Some <a href="Proxy_server" title="Proxy server">proxy servers</a> generate a 404 error when a <a href="List_of_HTTP_status_codes#5xx_server_errors" title="List of HTTP status codes">500-range error code</a> would be more correct. If the proxy server is unable to satisfy a request for a page because of a problem with the remote host (such as hostname resolution failures or refused TCP connections), this should be described as a 5xx Internal Server Error, but might deliver a 404 instead. This can confuse programs that expect and act on specific responses, as they can no longer easily distinguish between an absent web server and a missing web page on a web server that is present.

</p>

<div class="mw-heading mw-heading3"><h3 id="Intentional_404s">Intentional 404s</h3></div>

<p>In July 2004, the UK telecom provider <a href="BT_Group" title="BT Group">BT Group</a> deployed the <a href="Cleanfeed_(content_blocking_system)" title="Cleanfeed (content blocking system)">Cleanfeed</a> content blocking system, which returns a 404 error to any request for content identified as potentially illegal by the <a href="Internet_Watch_Foundation" title="Internet Watch Foundation">Internet Watch Foundation</a>.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> Other ISPs return a <a href="HTTP_403" title="HTTP 403">HTTP 403</a> "forbidden" error in the same circumstances.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> The practice of employing fake 404 errors as a means to conceal <a href="Censorship" title="Censorship">censorship</a> has also been reported in <a href="Thailand" title="Thailand">Thailand</a><sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> and <a href="Tunisia" title="Tunisia">Tunisia</a>.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> In Tunisia, where censorship was severe before the <a href="Tunisian_Revolution" class="mw-redirect" title="Tunisian Revolution">2011 revolution</a>, people became aware of the nature of the fake 404 errors and created an imaginary character named "<a href="Ammar_404" class="mw-redirect" title="Ammar 404">Ammar 404</a>" who represents "the invisible censor".<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup>

</p>

<div class="mw-heading mw-heading2"><h2 id="Microsoft_Internet_Server_404_substatus_error_codes">Microsoft Internet Server 404 substatus error codes</h2></div>

<p>The webserver software developed by Microsoft, <a href="Internet_Information_Services" title="Internet Information Services">Microsoft's Internet Information Services</a> (IIS), returns a set of substatus codes with its 404 responses. The substatus codes take the form of decimal numbers appended to the 404 status code. The substatus codes are not officially recognized by <a href="Internet_Assigned_Numbers_Authority" title="Internet Assigned Numbers Authority">IANA</a> and are not returned by non-Microsoft servers.

</p>

<div class="mw-heading mw-heading3"><h3 id="Substatus_codes">Substatus codes</h3></div>

<p>Microsoft's IIS 7.0, IIS 7.5, and IIS 8.0 servers define the following HTTP substatus codes to indicate a more specific cause of a 404 error:

</p>

<ul><li>404.0 – Not found.</li>

<li>404.1 – Site Not Found.</li>

<li>404.2 – <a href="ISAPI" class="mw-redirect" title="ISAPI">ISAPI</a> or <a href="Common_Gateway_Interface" title="Common Gateway Interface">CGI</a> restriction.</li>

<li>404.3 – <a href="MIME" title="MIME">MIME</a> type restriction.</li>

<li>404.4 – No handler configured.</li>

<li>404.5 – Denied by request filtering configuration.</li>

<li>404.6 – Verb denied.</li>

<li>404.7 – File extension denied.</li>

<li>404.8 – Hidden namespace.</li>

<li>404.9 – File attribute hidden.</li>

<li>404.10 – Request header too long.</li>

<li>404.11 – Request contains double escape sequence.</li>

<li>404.12 – Request contains high-bit characters.</li>

<li>404.13 – Content length too large.</li>

<li>404.14 – Request URL too long.</li>

<li>404.15 – Query string too long.</li>

<li>404.16 – DAV request sent to the static file handler.</li>

<li>404.17 – Dynamic content mapped to the static file handler via a wildcard MIME mapping.</li>

<li>404.18 – Query string sequence denied.</li>

<li>404.19 – Denied by filtering rule.</li>

<li>404.20 – Too Many URL Segments.</li></ul>

<div class="mw-heading mw-heading2"><h2 id="Custom_error_pages">Custom error pages</h2></div>

<p><a href="Web_server" title="Web server">Web servers</a> can typically be configured to display a customised 404 error page, including a more natural description, the parent site's branding, and sometimes a site map, a search form or 404-page widget. The protocol level phrase, which is hidden from the user, is rarely customized. <a href="Internet_Explorer" title="Internet Explorer">Internet Explorer</a>, however, will not display custom pages unless they are larger than 512 bytes, opting instead to display a "friendly" error page.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> <a href="Google_Chrome" title="Google Chrome">Google Chrome</a> included similar functionality, where the 404 is replaced with alternative suggestions generated by Google algorithms, if the page is under 512 bytes in size.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> Another problem is that if the page does not provide a <a href="Favicon" title="Favicon">favicon</a>, and a separate custom 404-page exists, extra traffic and longer loading times will be generated on every page view.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup>

</p><p>Many organizations use 404 error pages as an opportunity to inject humor into what may otherwise be a serious website. For example, Metro UK shows a polar bear on a skateboard, and the web development agency Left Logic has a simple drawing program.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> During the <a href="2015_United_Kingdom_general_election" title="2015 United Kingdom general election">2015 UK general election</a> campaign the main political parties all used their 404 pages to either take aim at political opponents or show relevant policies to potential supporters.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> In Europe, the <a href="NotFound_project" class="mw-redirect" title="NotFound project">NotFound project</a>, created by multiple European organizations including <a href="Missing_Children_Europe" title="Missing Children Europe">Missing Children Europe</a> and <a href="Child_Focus" title="Child Focus">Child Focus</a>, encourages site operators to add a <a href="Snippet_(programming)" title="Snippet (programming)">snippet of code</a> to serve customized 404 error pages<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> which provide data about <a href="Missing_children" class="mw-redirect" title="Missing children">missing children</a>.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup>

</p><p>While many websites send additional information in a 404 error message—such as a link to the <a href="Homepage" class="mw-redirect" title="Homepage">homepage</a> of a website or a search box—some also endeavor to find the correct web page the user wanted. Extensions are available for some <a href="Content_management_system" title="Content management system">content management systems</a> (CMSs) to do this.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup>

</p>

<div class="mw-heading mw-heading2"><h2 id="Tracking_404_errors">Tracking 404 errors</h2></div>

<p>A number of tools exist that crawl through a website to find pages that return 404 status codes. These tools can be helpful in finding links that exist within a particular website. The limitation of these tools is that they only find links within one particular website, and ignore 404s resulting from links on other websites. As a result, these tools miss out on 83% of the 404s on websites.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> One way around this is to find 404 errors by analyzing external links.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup>

</p><p>One of the most effective ways to discover 404 errors is by using <a href="Google_Search_Console" title="Google Search Console">Google Search Console</a>, <a href="Google_Analytics" title="Google Analytics">Google Analytics</a> or crawling software.

</p><p>Another common method is tracking traffic to 404 pages using log file analysis.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> This can be useful to understand more about what 404s users reached on the site. Another method of tracking traffic to 404 pages is using JavaScript-based traffic tracking tools.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup>

</p>

/* start https://en.wikipedia.org/ */

.mw-parser-output .portalbox{padding:0;margin:0.5em 0;display:table;box-sizing:border-box;max-width:175px;list-style:none}.mw-parser-output .portalborder{border:1px solid var(--border-color-base,#a2a9b1);padding:0.1em;background:var(--background-color-neutral-subtle,#f8f9fa)}.mw-parser-output .portalbox-entry{display:table-row;font-size:85%;line-height:110%;height:1.9em;font-style:italic;font-weight:bold}.mw-parser-output .portalbox-image{display:table-cell;padding:0.2em;vertical-align:middle;text-align:center}.mw-parser-output .portalbox-link{display:table-cell;padding:0.2em 0.2em 0.2em 0.3em;vertical-align:middle}@media(min-width:720px){.mw-parser-output .portalleft{margin:0.5em 1em 0.5em 0}.mw-parser-output .portalright{clear:right;float:right;margin:0.5em 0 0.5em 1em}}

/* end https://en.wikipedia.org/ */

</style>

<ul><li><a href="Blue_screen_of_death" title="Blue screen of death">Blue screen of death</a></li>

<li><a href="Funky_caching" title="Funky caching">Funky caching</a></li>

<li><a href="List_of_HTTP_status_codes" title="List of HTTP status codes">List of HTTP status codes</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

/* start https://en.wikipedia.org/ */

.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}

/* end https://en.wikipedia.org/ */

</style><div class="reflist">

/* start https://en.wikipedia.org/ */

.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("./mw/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("./mw/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("./mw/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("./mw/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}

/* end https://en.wikipedia.org/ */

</style><cite id="CITEREFFieldingReschke2014" class="citation cs1">Fielding, R; Reschke, J, eds. (June 2014). <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc7231#section-6.5.4">"404 Not Found"</a>. <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc7231"><i>HTTP/1.1 Semantics and Content</i></a>. Internet Engineering Task Force (IETF). sec. 6.5.4. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.17487%2FRFC7231">10.17487/RFC7231</a></span>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:14399078">14399078</a>. <a href="Request_for_Comments" title="Request for Comments">RFC</a> <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc7231">7231</a><span class="reference-accessdate">. Retrieved <span class="nowrap">13 December</span> 2018</span>.</cite></span>

</li>

<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><cite id="CITEREFZiv_Bar-YossefAndrei_Z._BroderRavi_KumarAndrew_Tompkins2004" class="citation book cs1">Ziv Bar-Yossef; Andrei Z. Broder; Ravi Kumar; Andrew Tompkins (2004). "Sic transit gloria telae". <i>Proceedings of the 13th international conference on World Wide Web</i>. pp. <span class="nowrap">328–</span>337. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F988672.988716">10.1145/988672.988716</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-1581138443</bdi>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:587547">587547</a>.</cite></span>

</li>

<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20140715000803/http://help.yahoo.com/l/nl/yahoo/ysearch/slurp/slurp-10.html">"Why is your crawler asking for strange URLs that have never existed on my site?"</a>. Yahoo Ysearch Help page. Archived from <a rel="nofollow" class="external text" href="http://help.yahoo.com/l/nl/yahoo/ysearch/slurp/slurp-10.html">the original</a> on 15 July 2014<span class="reference-accessdate">. Retrieved <span class="nowrap">4 September</span> 2013</span>.</cite></span>

</li>

<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://googlewebmastercentral.blogspot.com/2008/08/farewell-to-soft-404s.html">"Farewell to soft 404s"</a>. Google Official Blog<span class="reference-accessdate">. Retrieved <span class="nowrap">20 September</span> 2008</span>.</cite></span>

</li>

<li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110513071912/https://publicaffairs.linx.net/news/?p=154">"LINX Public Affairs » Cleanfeed: the facts"</a>. Publicaffairs.linx.net. 10 September 2004. Archived from <a rel="nofollow" class="external text" href="https://publicaffairs.linx.net/news/?p=154">the original</a> on 13 May 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">6 March</span> 2011</span>.</cite></span>

</li>

<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://airbrake.io/blog/http-errors/403-forbidden-error">"DEMON – Error 403"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">14 June</span> 2012</span>.</cite></span>

</li>

<li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><cite id="CITEREFSambandaraksa2009" class="citation news cs1">Sambandaraksa, Don (18 February 2009). <a rel="nofollow" class="external text" href="http://www.bangkokpost.com/tech/technews/11872/the-old-fake-404-not-found-routine">"The old fake '404 Not Found' routine - Dead link"</a>. <i>Bangkok Post</i><span class="reference-accessdate">. Retrieved <span class="nowrap">12 September</span> 2010</span>.</cite></span>

</li>

<li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><cite id="CITEREFNoman2008" class="citation web cs1">Noman, Helmi (12 September 2008). <a rel="nofollow" class="external text" href="http://opennet.net/node/950">"Tunisian journalist sues government agency for blocking Facebook, claims damage for the use of 404 error message instead of 403"</a>. Open Net Initiative<span class="reference-accessdate">. Retrieved <span class="nowrap">21 November</span> 2010</span>.</cite></span>

</li>

<li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://advocacy.globalvoicesonline.org/2010/05/27/anti-censorship-movement-in-tunisia-creativity-courage-and-hope/">"Anti-censorship movement in Tunisia: creativity, courage and hope!"</a>. Global Voices Advocacy. 27 May 2010<span class="reference-accessdate">. Retrieved <span class="nowrap">28 August</span> 2010</span>.</cite></span>

</li>

<li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20101202044514/http://blogs.msdn.com/b/ieinternals/archive/2010/08/19/http-error-pages-in-internet-explorer.aspx">"Friendly HTTP Error Pages"</a>. msdn.com. 18 August 2010. Archived from <a rel="nofollow" class="external text" href="http://blogs.msdn.com/b/ieinternals/archive/2010/08/19/http-error-pages-in-internet-explorer.aspx">the original</a> on 2 December 2010<span class="reference-accessdate">. Retrieved <span class="nowrap">14 June</span> 2012</span>.</cite></span>

</li>

<li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1695">"Issue 1695: Chrome needs option to turn off "Friendly 404" displays"</a>. <i>bugs.chromium.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 December</span> 2021</span>.</cite></span>

</li>

<li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><cite id="CITEREFHeng2008" class="citation web cs1">Heng, Christopher (7 September 2008). <a rel="nofollow" class="external text" href="http://www.thesitewizard.com/archive/favicon.shtml">"What is Favicon.ico and How to Create a Favicon Icon for Your Website"</a>. <i>The Site Wizard</i><span class="reference-accessdate">. Retrieved <span class="nowrap">23 February</span> 2011</span>.</cite></span>

</li>

<li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://internetfolks.com/dastardly-favicon-ico-found-error/">"The Dastardly "favicon.ico not found" Error"</a>. <i>Internet Folks</i>. 3 August 1999.</cite></span>

</li>

<li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><cite class="citation news cs1"><a rel="nofollow" class="external text" href="http://metro.co.uk/2013/04/16/from-skateboarding-bears-to-missing-children-the-power-of-the-404-not-found-error-page-3591031/">"From skateboarding bears to missing children: The power of the 404 Not Found error page"</a>. Metro. 6 June 2011<span class="reference-accessdate">. Retrieved <span class="nowrap">16 April</span> 2013</span>.</cite></span>

</li>

<li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.bbc.co.uk/newsbeat/article/32480181/the-political-page-404-war">"The political Page 404 war"</a>. <i>BBC Newsbeat</i>. 27 April 2015<span class="reference-accessdate">. Retrieved <span class="nowrap">18 May</span> 2018</span>.</cite></span>

</li>

<li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20140902081543/http://notfound.org/notfound">"Notfound.org"</a>. <i>notfound</i>. Archived from <a rel="nofollow" class="external text" href="http://notfound.org/notfound">the original</a> on 2 September 2014.</cite></span>

</li>

<li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text"><cite class="citation news cs1"><a rel="nofollow" class="external text" href="https://www.bbc.com/news/technology-19741350">"Missing children messages go on 404 error pages"</a>. <i><a href="BBC_News" title="BBC News">BBC News</a></i>. 27 September 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">20 September</span> 2014</span>.</cite></span>

</li>

<li id="cite_note-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-18">^</a></b></span> <span class="reference-text"><cite id="CITEREFSwenson2008" class="citation web cs1">Swenson, Sahala (19 August 2008). <a rel="nofollow" class="external text" href="http://googlewebmastercentral.blogspot.com/2008/08/make-your-404-pages-more-useful.html">"Make your 404 pages more useful"</a>. <i>Official Google Webmaster Central Blog</i>. Google, Inc<span class="reference-accessdate">. Retrieved <span class="nowrap">28 August</span> 2009</span>.</cite></span>

</li>

<li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://springtrax.com/key-stats-about-404-errors/default.htm#/section4">"Sources Leading To 404s"</a>. SpringTrax<span class="reference-accessdate">. Retrieved <span class="nowrap">11 February</span> 2013</span>.</cite></span>

</li>

<li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text"><cite id="CITEREFCushing2013" class="citation web cs1">Cushing, Anne (2 April 2013). <a rel="nofollow" class="external text" href="http://searchengineland.com/a-data-centric-approach-to-identifying-404-pages-worth-saving-152844">"A Data-Centric Approach To Identifying 404 Pages Worth Saving"</a>. Search Engine Land<span class="reference-accessdate">. Retrieved <span class="nowrap">7 June</span> 2013</span>.</cite></span>

</li>

<li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.404errorpages.com/#tracking">"Tracking and Preventing 404 Errors"</a>. 404errorpages.com<span class="reference-accessdate">. Retrieved <span class="nowrap">7 June</span> 2013</span>.</cite></span>

</li>

<li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://springtrax.com/how-springtrax-helps/understand-your-websites-404-errors.htm">"Understand 404 Errors"</a>. SpringTrax.com<span class="reference-accessdate">. Retrieved <span class="nowrap">7 June</span> 2013</span>.</cite></span>

</li>

</ol></div></div>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="http://alistapart.com/article/amoreuseful404">A More Useful 404</a></li>

<li><cite class="citation cs1"><a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc7231#section-6.5.4">"404 Not Found"</a>. <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc7231"><i>Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content</i></a>. <a href="Internet_Engineering_Task_Force" title="Internet Engineering Task Force">Internet Engineering Task Force</a>. sec. 6.5.4. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.17487%2FRFC7231">10.17487/RFC7231</a></span>. <a href="Request_for_Comments" title="Request for Comments">RFC</a> <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc7231">7231</a>.</cite></li>

<li><a rel="nofollow" class="external text" href="https://httpd.apache.org/docs/2.4/mod/core.html#errordocument">ErrorDocument Directive</a> – instructions on custom error pages for the <a href="Apache_HTTP_Server" title="Apache HTTP Server">Apache 2.0 web server</a></li>

<li><a rel="nofollow" class="external text" href="http://www.ovff.org/pegasus/songs/404-not-found.html">404: Not Found</a> – an award-winning <a href="Filk" class="mw-redirect" title="Filk">filk</a> song about the error code</li></ul>

/* start https://en.wikipedia.org/ */

.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output .navbox-group{white-space:nowrap;text-align:right}.mw-parser-output .navbox,.mw-parser-output .navbox-subgroup{background-color:#fdfdfd}.mw-parser-output .navbox-list{line-height:1.5em;border-color:#fdfdfd}.mw-parser-output .navbox-list-with-group{text-align:left;border-left-width:2px;border-left-style:solid}.mw-parser-output tr+tr>.navbox-abovebelow,.mw-parser-output tr+tr>.navbox-group,.mw-parser-output tr+tr>.navbox-image,.mw-parser-output tr+tr>.navbox-list{border-top:2px solid #fdfdfd}.mw-parser-output .navbox-title{background-color:#ccf}.mw-parser-output .navbox-abovebelow,.mw-parser-output .navbox-group,.mw-parser-output .navbox-subgroup .navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}

/* end https://en.wikipedia.org/ */

</style></div><div role="navigation" class="navbox" aria-labelledby="Error_messages90" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><div id="Error_messages90" style="font-size:114%;margin:0 4em"><a href="Error_message" title="Error message">Error messages</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">System failure</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="Fatal_system_error" title="Fatal system error">Fatal system error</a></li>

<li><a href="Guru_Meditation" title="Guru Meditation">Guru Meditation</a></li>

<li><a href="Kernel_panic" title="Kernel panic">Kernel panic</a></li>

<li><a href="Linux_kernel_oops" title="Linux kernel oops">Linux kernel oops</a></li>

<li><a href="Xbox_360_technical_problems" title="Xbox 360 technical problems">Red Ring of Death</a></li>

<li><a href="Screen_of_death" class="mw-redirect" title="Screen of death">Screen of death</a>

<li><a href="Black_screen_of_death" title="Black screen of death">Black</a></li></ul></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Application failure</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Abnormal_end" class="mw-redirect" title="Abnormal end">ABEND</a></li>

<li><a href="Fatal_exception_error" title="Fatal exception error">Fatal exception error</a></li>

<li><a href="Segmentation_fault" title="Segmentation fault">Segmentation fault</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Device and data errors</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="Not_a_typewriter" title="Not a typewriter">Not a typewriter</a></li>

<li><a href="PC_LOAD_LETTER" title="PC LOAD LETTER">PC LOAD LETTER</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Abort%2C_Retry%2C_Fail%3F" title="Abort, Retry, Fail?">Abort, Retry, Fail?</a></li>

<li><a href="Bad_command_or_file_name" title="Bad command or file name">Bad command or file name</a></li>

<li><a href="Halt_and_Catch_Fire_(computing)" title="Halt and Catch Fire (computing)">Halt and Catch Fire</a></li>

<li><a href="Out_of_memory" title="Out of memory">Out of memory</a></li>

<li><a href="Does_not_compute" title="Does not compute">Does not compute</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Lists</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="List_of_HTTP_status_codes" title="List of HTTP status codes">List of HTTP status codes</a></li>

<li><a href="List_of_FTP_server_return_codes" title="List of FTP server return codes">List of FTP server return codes</a></li>

<li><a href="List_of_SMTP_server_return_codes" title="List of SMTP server return codes">List of SMTP server return codes</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Spinning_pinwheel" title="Spinning pinwheel">Spinning pinwheel</a></li>

<li><a href="Windows_wait_cursor" title="Windows wait cursor">Windows wait cursor</a></li>

<li><a href="2024_CrowdStrike-related_IT_outages" title="2024 CrowdStrike-related IT outages">2024 CrowdStrike-related IT outages</a></li></ul>

</div></td></tr></tbody></table></div></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2025-06-03" href="https://en.wikipedia.org/wiki/?title=HTTP_404&oldid=1293831813">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

</div>

</div></div>

</div>

</main>

</div>

</body></html>