Here's a version that works with both IE and FF.
I redone everything because a lot of what you did wasn't really needed.
Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Forum66 - Simple Solutions For Your Website</title>
<style type="text/css" media="screen">
body {
margin: 0 auto;
text-align: center;
background: url(images/bg.jpg) repeat-x;
background-attachment: fixed;
font-family: Tahoma;
font-size: 10pt; /* I personally use pt instead of px for font, I believe it works better with font. */
color: #808080;
line-height: 12px;
}
p, li, ul, h1, h2, h3, img {
padding: 0;
border: 0;
margin: 0;
}
a, a:visited {
color: #808080;
text-decoration: underline;
}
/* Wrapper - Container */
#wrapper {
width: 760px;
background-color: #fff;
margin: 0 auto;
text-align: left;
}
/* Header */
#header_nav {
height: 39px;
background: url(images/tnav_bg.jpg) repeat-x;
}
.nav_home {
margin-left: 19px;
}
.nav_contact {
margin-left: 39px;
margin-right: 71px;
}
</style>
</head>
<body>
<!-- Wrapper / Container -->
<div id="wrapper">
<!-- Header Navigation -->
<div class="header_nav"><a href=""><img class="nav_home" src="http://www.visualesq.com/clients/Forum66/images/tnav_home.jpg" alt="" /></a><a href=""><img class="nav_contact" src="http://www.visualesq.com/clients/Forum66/images/tnav_cont.jpg" alt="" /></a><img src="http://www.visualesq.com/clients/Forum66/images/header_t.jpg" alt="" /></div>
<!-- Header Banner / Logo -->
<div class="header_banner"><img src="http://www.visualesq.com/clients/Forum66/images/header_main.jpg" alt="" /></div>
</div>
</body>
</html>