Thread:Project:Support desk/Wrong displayyin on some pages/reply

You are using the Vector skin and the problem is not present on all pages, but only on some. The Main_Page e.g. displays just fine. So I guess this is caused by some HTML elements in your page. For these elements, you obviously have CSS styles, which break the design; these styles might e.g. be in MediaWiki:Common.css or in MediaWiki:Vector.css.

If you have upgraded from MediaWiki 1.24.x to 1.25, then you can check these commits to see, what was actually changed.