You've got a table with a background image: <table align="left" background="index.php_files/nav_back.gif" border="0" height="594" width="58%">
I think you'll find that that 'background' is not a valid attribute within 'table'. If you delete that, the line disappears. Some browsers are rendering and some aren't. I can't understand the reason why two IE browsers should be different though!