<!DOCTYPE HTML PUBLIC "-//W3C// DTD HTML 4.0//EN">
<head><meta http-equiv="Content-Type" content="text/html; charset=windows-1251" />
<title> Проверяем </title>
<style type="text/css">
#layer1 {
background-color: red;
width: 100%;
height: 165px;
position: absolute;
left: 0px;
top: 0px;
z-index: 1;
visibility: visible;
}
</style>
<script langvage="JavaScript" type="text/javascript" >
var layer1 = document.getElementById('layer1')
layer1.style.width = '50%'
</script>
</head>
<body>
<div id="layer1"> </div>
</body>
</html>