Adding Header and left columns

[dar]

Hi,
I am developing a custom theme.

1. What are the pros/cons of using layers vs tables? (By header I mean a 100% header above the forum where I can put advertising).

I will eventually have a front page (well, it exists at the moment but only to immediately pass invisibly into the forum).

2. For search engines is it best top have the meta tags on the first page or both the first page and in the forum?

Many thanks

dar