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 the interwiki prefix, if any) in the search box.
Possible causes are:
an attempt to load a URL such as https:/wiki/| (the | character is unsupported);
an attempt to load a URL pointing to a "non-local" interwiki page (usually those not run by the Wikimedia Foundation). For example, the URL https:/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 https:/wiki/meta:Main_page can be used to load meta:Main_page. All interlanguage prefixes are marked as local, and thus URLs such as https:/wiki/fr:Accueil will work as expected. However, non-local interwiki pages can still be accessed by interwiki linking or by entering them in the search box. For example [[meatball:WikiPedia]] can be used on a page, like this: meatball:WikiPedia.