That would be /index.php?title=MediaWiki:Noarticletext (which you can easily get at via /index.php?title=Special:Specialpages and search for the string, "There is currently no text...," but it's not really a 404 message - its a wiki message. I think you have to have server tinker-tailor-soldier-spy access rights to customize the pages thrown by the server.
Stabatha Cogsprocket wrote:
Also where do I edit the template for a more custom 404 rather the the default of There is currently no text in this page.... within MediaWiki.