div表格如何居顶，求大侠指导

div表格怎么居顶，求大侠指导
<style type="text/css">
body {
font-family: "Times New Roman", "宋体", arial;
font-size: 12px;
margin:0 auto;
text-align: center;
background-image: url(../../images/background_top_0.png)
}
a:link, visited, hover, active {
text-decoration: none;
color: #000000;
}
#header {
position:relative;
margin-top:0px;
width: 1440px;
height: 196px;

}
#header-top {
position:relative;
margin-top:0px;
width: 1440px;
height: 30px;

background-image: url(images/background_0.png)
}
#box-top {
position:relative;
margin-top:0px;
left: 200px;
width: 920px;
height: 30px;
}
</style>
<div id="header">
<div id="header-top"  >
  <div id="box-top">
    <div style="text-align:right; font-family:verdana; font-size:12px; margin-top:6px; "> 
    <a href="*">HOME    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</a> 
    <a href="*">ABOUT&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</a> 
    <a href="*">CASE&nbsp;&nbsp;&nbsp;    &nbsp;&nbsp; </a> 
    <a href="*">CONTACT</a> 
    </div>
  </div>
</div>
</div>

灰色的背景能居顶对齐
[解决办法]
外面加个大的div，然后width100%，height100%。OK