Manual:$wgSiteSupportPage

Details
If non-blank, this gives the title of the support page for your wiki.

This can be used for whatever you like, for example to ask for donations or to provide contact details.

This has been superseded in later versions by the   setting and the "MediaWiki:" namespace. See sidebar>Special:MyLanguage/Manual:Interface/Sidebar|Manual:Interface/Sidebar for more information.