Oh well. I'll try to fix things up. I hope I can get this done in time :(
You need to decide on a DocType - you won't get any decent validation feedback until you do. 4.01 Transitional should be fine.
Odd - it appears perfect on IE -
You can get away with a lot of sloppy stuff in IE... which seems very helpful until you realise that it's taught you to write rubbish HTML. (Been there, done that!)
EDIT: Some of this might come in useful...
http://www.positioniseverything.net/index.php