Unwanted gap and how to make page 100% height always

[Rob100]

It's my 2nd post to please be kind

I'm just playing with the shop layout. Ignore the header (logo) it's only a temp mock-up to give me the idea.

2 questions...

1) How can I remove the gap between the header (logo) and the "tabs"?

2) How can I force the page to always we 100% the height of the window and keep the footer at the bottom of the page?

The attached (very quick photoshop hack 'n paste) should give you an idea of what I'm trying to achieve.

Thanks,

Rob.