Manual:$wgStylePath

Details
The URL of the skins directory.

This is where MediaWiki tells the browser to get the styles from.

For wiki families with multiple languages, it may be a good idea to set this URL, in all your wiki languages, to just one directory or server.

That way the browser will only have to load the css>Special:MyLanguage/Manual:CSS|CSS once for every wiki.

If you change where on your filesystem the skins directory is, you may also have to change  .

  only controls where the browser gets the styles from, not where MediaWiki looks for the style files.