IE and Netscape will both recognize the height=100% attribute in your table tag BUT ONLY in the outermost table. No "nested" table will see it in Netscape though. But you can still make nested tables with pixel heights.

Also, if you have a table with the height=40...

...and then right below that table you have a table of height=100%, that will push the push the bottom 100% table 40 pixels past the bottom margin.