How to fix the size for different resolution

I have left,middle and right DIV. my middle DIV will show table which getting result from Mysql query. If the table size shown is smaller than the middle div,
then everythng is fine.

however, when i change my resolution to 800*600, the table size will
bigger than the middle div and cause the middle div out of its place.
i have try position=fixed, auto, relative but none of them solve the
problem.

so, how to fix this problem?

Thanx.