Forum:Some javascript help needed here

By using javascript, how can I add the class: mainpagehover to the wordmark? The source containing for the css class should be  Home Searching for more? Return to the Main Page easily and start searching for more!  If you don't understand, then please reply &mdash; [/wiki/User:Sam_Wang S a m ] [/wiki/User_talk:Sam_Wang W a n g ] 04:29, March 18, 2012 (UTC)