Probably something simple I'm not aware of. IE7 isn't playing nice and text is moving completely outside of bounds. Thanks so much in advance!
div#wrapper_header has a height of 174px while the
div#header_top has a similar height BUT with a top margin of 100px.
This causes the second root table to stack at the offset of
top: 174px while the content of the first root table overflowed down. This could be an IE7 specific bug.
You can fix it by specify the
div#wrapper_header height to 'auto' or simply do not set any value.
PS: The current markup might not render properly in IE6.
Try just remove margin assigned to header_top and assign it to body in padding-top.