为什么我这个清除浮动没有效果？

<!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=utf-8" />
<title>无标题文档</title>
<style type="text/css">
* {
    margin:0;
   padding:0;
}
#wrap {
   background:#00C;
   margin:0 auto;
   width:960px;
}
#header {
   background:#FF3300;
   width:100%;
}
#mainbody{
        background:#FC0;
        width:100%;
        overflow：hidden；}

.left {
   width:800px;
   height:200px;
   background:#000;
    float:left;

}
.right {
width:140px;
height:500px;
background:#690;
float:left;
}
#footer {
   background:#639;
   width:100%;
}
</style>
</head>

<body>
<div id="wrap">
<div id="header">头部</div>
<div id="mainbody">
    <div class="left"></div>
    <div class="right"></div>
</div>
<div id="footer">版权部分</div>
</div>
</body>
</html>