Dead link
A dead or defective reference (English link ) or Totlink or English Dead link is a hyperlink in the World Wide Web , which is present on a (no longer) resource (such as a website or file ) shows. When the URI is selected , the web server usually delivers a response with the HTTP status code 404 Not Found (the requested resource could not be found) or 410 Gone (the resource no longer exists).
References to non-existent passages are also known from printed reference works .
causes
Dead links are a hitherto unsolved problem of hypertext and can essentially be traced back to the fact that the Internet is a decentralized network . Therefore, the integrity of the same can never be ensured.
The reasons for the existence of dead links can be very different and, above all, occur in very different places. Reasons often encountered in practice include:
- The file referenced by the URL has been moved, renamed, or deleted.
- The link on the original page is incorrectly specified, for example the upper or lower case in the path (URIs are case sensitive in certain places ).
- The domain you are looking for has now been assigned to a registrar and the website itself is still without any content.
- The web server is no longer available, for example because of network problems or because the computer is switched off.
- The host or domain name does not exist (anymore) or cannot be resolved in the DNS .
The respective creators of the website are responsible for errors in internal links. If the system (e.g. in a content management system ) does not automatically display the dead links, these can be tracked down with the help of tools.
impact
The problem with URLs that no longer exist is essentially due to the fact that linked pages are not or cannot be informed of the non-existence. This applies in particular to external links that are in a different domain . Search engines in particular have often indexed websites that have not existed for weeks or months. Some search engines continue to cache the content for some time .
Dead links also affect the quality of search results for search engines. In some calculation methods of PageRank , a method introduced by the search engine operator Google to determine the quality of websites, dead links play a role (solution of an eigenvector problem ) and are first removed before the calculation. Usually, however, they are reinserted in the last step of the numerical iteration process, so that a PageRank is also assigned to these pages .
The English term link rot (for example: "link rot") has become established for URLs becoming invalid over time . There are various estimates of the extent: A study of digital libraries showed that around 3% of the objects were no longer accessible after one year. The bookmarking website Pinboard reported in 2014 that it was seeing a fairly stable link red rate of 5% per year.
possible solutions
One option that is more likely to combat the symptoms of dead links is the Internet Archive's Wayback Machine . Chronological copies of web pages can be used to grant access to web pages, some of which no longer exist in the original.
On the other hand, bodies like the W3C with the Cool URIs don't change campaign, which are intended to raise awareness of the need for fixed URLs among the creators and administrators of websites, are combating the causes . One solution is to dynamically link, e.g. B. subdomains or directory names can be used. In addition, there are already systems that pursue the goal of fixed URLs by automatically creating a redirect such as a Persistent Uniform Resource Locator .
Development of the error code "404"
The error code "404" is said to have arisen because, in the early days of the Internet, the server, which caused this error due to missing files, was in room 404 at CERN , where the origin of the World Wide Web can be found. However, this story can be classified as a modern legend and goes back to a hoax . In reality, the error code is not based on a living story like this, but is just one error code among a total of 27 different ones that are defined as “ client errors ” in the HTTP standard . All HTTP status codes have three digits, client error status codes start with the number "4", so "404" is the fifth registered client error.
Trivia
In 2007 in Nagoya , Japan , an emoband named itself after the error code: 404 Not Found .
The diocese of Essen amusingly points out links that cannot be reached:
See also
- Hanging pointer as a general concept in computer science
Web links
- w3.org - Status Code Definitions - Status code definition
Individual evidence
- ↑ Heise RegioConcept March 22, 2017: Every dead link is a small coffin nail for your website! , accessed September 7, 2017
- ↑ Michael L. Nelson, B. Danette Allen: Object Persistence and Availability in Digital Libraries . In: D-Lib Magazine . 8, No. 1, 2002. doi : 10.1045 / january2002-nelson .
- ↑ Maciej Cegłowski: Web Design: The First 100 Years ( English ) September 9, 2014. Accessed July 22, 2015.
- ↑ http://www.w3.org/Provider/Style/URI (English)
- ^ Story of 404. In: plinko.net. Retrieved June 7, 2018 .
- ↑ HTTP / 1.0 Room 404 Object Not Found. In: room404.com. Retrieved June 7, 2018 .
- ^ Anna Wiener: Page not found: a brief history of the 404 error. In: Wired.com. April 12, 2017. Retrieved June 6, 2018 .
- ↑ https://www.bistum-essen.de/glaube-einfach/start/politik-wirtschaft-soziales/heinrich-brauns-preis/