Then leave it out. The technique is still the same.
The only real solution to your problem using 2 tables is to use the table-layout:fixed algorithm (applied to the table element) and then give a width to each cell in both tables (both tables must be the same and then they will obey the widths that are set). It is not possible to make 2 unrelated elements keep track with each other automatically.
In the link TechnoBear gave one of the first methods mentioned (without js) will work for fluid width table headers but comes with a few caveats, Read the thread for more details.
In the end the only real wy to do this effectively is with js and there are plenty of examples in that thread or on the web that can accomplish this (mine is better than most but all come at a price in one way or another).