Wikipedia:Bad title/sandbox

The requested page title is invalid. It may be empty, contain unsupported characters, or include a non-local or incorrectly linked interwiki prefix. You may be able to locate the desired page by searching for its name (with interwiki prefix, if any) in the search box.

Possible causes are:
 * an attempt to follow a link to a diff for a page that has since been deleted;
 * an attempt to load a URL such as http://en.wikipedia.org/wiki/| (the | character is not permitted in page titles);
 * an attempt to load a URL pointing to a "non-local" interwiki page. For example, the URL http://en.wikipedia.org/wiki/meatball:WikiPedia will give this error, because the "meatball:" interwiki prefix is not marked as local in the interwiki table. Certain interwiki prefixes are marked as local in the table. For example, the URL http://en.wikipedia.org/wiki/meta:Main_page can be used to load Main_page. All interlanguage prefixes are marked as local, and thus URLs such as http://en.wikipedia.org/wiki/fr:Accueil will work as expected.