Common.js and Common.css are pages which influence the interface and layout of Wikipedia.
Common.js may refer to one of several
JavaScript pages:
Wikipedia's sitewide "common JavaScript" page, located at
MediaWiki:Common.js. This is loaded for all users.
An individual user's "common JavaScript" page, located at
Special:MyPage/common.js. Unlike
Special:MyPage/skin.js, which redirects to the JavaScript page of the user's current
skin, a user's common.js page is loaded regardless of which skin they are using.
Wikipedia's sitewide "common CSS" page, located at
MediaWiki:Common.css. This is loaded for all users.
An individual user's "common CSS" page, located at
Special:MyPage/common.css. Unlike
Special:MyPage/skin.css, which redirects to the CSS page of the user's current
skin, a user's common.css page is loaded regardless of which skin they are using.