Anzeigefehler im FF2, im IE7 alles i.O. (floatfehler?)

@charset "utf-8";
/* CSS Document */




body {
    margin: 0px;
    background:#e0e0e0 url(bg.jpg) repeat-x;
    color:#FFFFFF;
}
#top {
height:140px;
/* background:url(bg.jpg) repeat-x; */
text-align:center;
border-bottom:5px solid #0b0b0b;
margin-bottom:60px;
}
#top h1 {
display:none;
}
#maintop {
margin-top:10px;
background:url(maintop.jpg) no-repeat center;
height:42px;
}
#main {
margin-left:auto;
margin-right:auto;
padding-left:20px;
padding-right:20px;
width:800px;
background:url(mainbg.jpg) repeat-y;
padding-bottom:7px;
}
#mainbot {
margin-bottom:10px;
background:url(mainbot.jpg) no-repeat center;
height:55px;
padding-top:5px;
color:#CCCCCC;
width:840px;
margin-left:auto;
margin-right:auto;
text-align:center;
}
#mainbot a, #mainbot a:visited {
color:#FF9900;
text-decoration:none;
}
#mainbot a:hover {
color:#FFFFFF;
}
#left {
float:left;
width:150px;
margin-left:1px;
margin-right:2px;
border-right:1px solid #4e4e4e;
}
#cont {
float:right;
width:640px;
margin-right:1px;
}