HTTP 404 Error Page

In 2008, a study found that "404" had become a slang synonym for "clueless" in the UK/Ireland areas. Slang lexicographer Jonathon Green said that "404" as a slang term had been driven by the "influence technology" and young people, but at the current time, such usage was relatively confined to London and other urban areas. The study, carried out by the telecommunications arm the Post Office, concluded that writing abbreviations such as "404" was expedient to the sender, while an Australian study found that such phrases impaired the intelligibility the message.
While many websites send additional information in a 404 error message—such as a link to the homepage a website or a search box—there are also much more advanced extensions available as widgets that endeavor to find the correct web page the user wanted.