IE / Firefox Placement Problem

[Guest bewild]

I am editing our Yahoo store check out manager. I created everything in firefox and it works fine. You can view the page here: http://order.store.yahoo.net/cgi-bin/wg-or...t-2420193029716But when I look at it in Internet Explorer it displays the "body" or "cart" below my sidebar. Any help is appreciated. I have been trying to fix the code for days but haven't figured it out. Here is the CSS code I've been using if you can not view the site and view source:<style type="text/css">#ys_pageBody{ width:600px; position:relative; }.mainnav, .nav{width:150px;border-right: 1px dashed #acc2d9;margin-right:5px}#ys_pageBody.ys_sideBar { border-left:none;}.mainnav a{ font: bold 11px Tahoma, Verdana; color: #003298; text-decoration:none; display:block; border-bottom:1px solid #C2D0D8; text-align:right; padding:5px 15px 5px 5px;}* html .nav a:hover, * html .mainnav a:hover{ width:100%}.nav a{ font:11px Tahoma, Verdana; color: #0A4565; text-decoration:none; /*background-image:url(/lib/stylespilotshop/nav-bg1.gif);*/ padding:5px 15px 5px 5px; display:block; text-align:right;}.nav a:hover{ text-decoration:underline; color:#ffa411; /*background-image:url(/lib/stylespilotshop/nav-bg2.gif); background-repeat:no-repeat*/}#header{ position:relative; width:100%;}.style1 {font-family: Tahoma, Verdana;font-size: 10px;color: #7199AF; text-decoration:none}.style1 a{ text-decoration:none;}.style2 {font-family: Tahoma, Verdana; font-size: 10px; color: #0A4565; text-decoration:none}.style3{position:absolute; top:5px; left:250px; color: #003399;}.style3 a{font:normal 10px Tahoma, Verdana; color: #003399; text-decoration:none;}.style3 a:hover {text-decoration:underline;}#ys_cart table.ys_basket{ border:1px solid #acc2d9 !important;}#ys_cart tr.ys_head th.l{ background-color:#acc2d9 !important; font-size:10px !important;}#ys_pageBody #ys_buyerInfo{ border:1px solid #acc2d9 !important;}.ys_majorSection h3{ background-color:#acc2d9 !important; font-size:10px !important;}.ys_majorSection h4{ font-size:10px !important;}</style><script type="text/javascript" src="https://lib.store.yahoo.net/lib/villagestreetwear/checkout-leftz1.php"></script>