Ok, just going through those.
1. How come? It should all be xhtml compatible.
2. Need 2 interactive ids so the link can be attributed to the image and the rollover can work.
3. There is white space around them, although not as much as is there. It was designed within Photoshop to fit perfectly in the size space with the images tightly packed together on the top table.
4. Didn't realise this in the code. What else could would I put to show the register button if the user was logged out?
5. Tried but didn't work

6. Table cells add up :S