Ran into a messy problem getting tables to expand to 100% of available height recently. Found this document that helps understand the problem and the solution:
http://www.apptools.com/examples/tableheight.php
Basically we need to set the height of the html/body to 100% then we can set the height of the tables to 100%.
html,body{
margin:0;
padding:0;
height:100%;
border:none
}