I have the following example:
Maybe this code help you...
I test it at jsfiddle: http://jsfiddle.net/mHTTM/5/
In IE, if you wearing 100 percent in child tag, width/height will be the same as the top parent tag's width/height. Not the parent tag. So you just need to change child tags from percent to pixel.
Text with an unknown height (22px here)