I don't know your plan, but I'll run through 2 examples.
1) You have a table at the top of the page with a blue graphic with a logo. Just add the property width=100% to the table and add a background color
that is the same as the blue graphic. No matter the size of the browser window, it will expand to fill the screen and show a blue bar all the way
across (don't forget to set the page margins to zero in the body tag and left or right justify the logo).
2) Now the layout table. Say it's 3 columns...left, middle, and right. I would make the left and right fixed size, like 200px for navigation and
advertising respectively. Then set the table to width=100% and the middle column (the page text) will size to full width no matter what browser is
looking at it.
Depending how complex the items are you plan to have in the middle, it will work. It does take some tweaking depending on the plan, but I think if you
want an easy method...it should work.