The World Wide Web has a very dynamic character with resources constantly disappearing and (re-)surfacing. A ubiquitous result is the "404 Page not Found" error as the request for missing web pages. We investigate tags obtained from Delicious for the purpose of rediscovering such missing web pages with the help of search engines. We determine the best performing tag based query length, quantify the relevance of the results and compare tags to retrieval methods based on a page's content. We find that tags are only useful in addition to content based methods. We further introduce the notion of "ghost tags", terms used as tags that do not occur in the current but did occur in a previous version of the web page. One third of these ghost tags are ranked high in Delicious and also occurred frequently in the document which indicates their importance to both the user and the content of the document.
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