[SOLVED] Rollover Graphic in Header

Hi! I'm not sure this is going to be an easy one because I've read everything in the forum I can find and seems like it gets complicated, but I would like to put a rollover logo in my header. It can go in the horizontal bar or the logo area itself, I just want to get it in there! I read this thread and tried inserting the javascript into the horizontal bar but it didn't work (because I don't know what I'm doing. Ran into syntax errors). There's a way to do it using CSS inserts and avoid using js altogether, right? I just need some advice to get rolling!