+2  A: 

Just use a cleverly placed background image. Then make sure your tab-bottoms sit flush "on top" of the bottom of your background-image.

Jonathan Sampson
so - just to make sure i understand - you think the bottom of their blue bar is just a tiled blue sliver image?and if so, what if i didn't want a solid background...would i think just have to make a super large background image to cover all browsers? (ie - if i want a floral effect or something).thanks a lot:)
johnnietheblack
+1  A: 

Like Jonathan Suggested, use a background image. But I'd like to add that you should make sure you know the difference between margin and padding, which is extremely important for Facebook's theme.

Chacha102
I do know the difference...but I am not sure what you are getting at as far as how it applies to this scenario? Please excuse my newbie-ness...
johnnietheblack
Facebook uses padding to make sure that any boxes that could reach the header background have a nice big white box around them for readability. But margin to make sure that the elements have division between the white space.
Chacha102
+3  A: 

I suggest that you use Firebug to look at their html / css markup.

Keltex