我有一个类似 twitter/facebook 的标题、一个固定的标题和一个主要内容。当我向下滚动到最后一行时，内容 div 与标题重叠。我怎样才能避免这种情况？
这是我页面的截图：
这是我的html的结构：
<body>
<div>
<?php include("initcontrols/header.php"); echo $plHeader;?>
</div>
<div id="mainform">
<noscript>It seems your browser doesn't support Javascript.<br /></noscript>
<!-- Apply blue theme as default for all tiles -->
<div id="tiles" class="blue">
<!-- Sliding Tile that shows 100% of the back tile every 3 seconds -->
<div class="live-tile" data-stops="100%" data-speed="750" data-delay="3000">
<span class="tile-title">slide tile (figure 2a)</span>
<div><img src="images/say.jpg" width="180" height="180" alt="1" /></div>
<div><img src="images/sayako.jpg" width="180" height="180" alt="2" /></div>
</div>
<!-- Red Flip Tile that flips every 4 seconds -->
<div class="red live-tile" data-mode="flip" data-delay="4000">
<div>
<img src="images/home.png" alt="3" />
<a class="tile-title">flip tile front (figure 2b)</a>
</div>
<div>
<img src="images/message.png" alt="4" />
<a class="tile-title">flip tile back (figure 2b)</a>
</div>
</div>
<script type="text/javascript">
// apply regular slide universally unless .exclude class is applied
// NOTE: The default options for each liveTile are being pulled from the 'data-' attributes
$(".live-tile, .flip-list").not(".exclude").liveTile();
</script>
</div>
我的CSS：
div#header{
padding-left:15px;
overflow:hidden;
position: fixed;
margin:0px;
top:0px;
left:0px;
display: block;
width: 100%;
height: 90px;
-moz-box-shadow: 0 1px 2px rgba(0, 0, 0, 0.5);
background:#333333;
background: -moz-linear-gradient(center top , #736F6E, #111111) repeat scroll 0 0 transparent;
}
div#header-title{
color: #FFF;
float: left;
display:inline-block;
}
div#header h2{
margin: 0 0 0 3px;
z-index:12;
}
div#header h1{
margin-top:0;
margin-bottom:0;
}
#mainform{
width:960px;
background: #F0F0F0;
border: 1px solid #CCC;
height: 2000px;
margin: 100px auto;
}
对于我的实时瓷砖外观： http: //pastebin.com/cpBXYVRu 我使用了http://www.drewgreenwell.com/projects/metrojs#applicationBar的模板：