Board Thread:Support Requests - Designing Your Wiki/@comment-6100947-20130216061643/@comment-1318845-20130216063521

You need to go into the source code and remove them by hand (which you should probably do anyways; the category module is rather unreliable).

In order to do that, you'll want to go into Special:Preferences and select "Disable Category module (only applies if visual mode editing is disabled)" then save and open up the editor for the main page again. Then, instead of the category module, there will be links to the categories at the bottom of the page. From there you can remove from the page to fix the problem.

Hope this helps.