firefox IE7 布局问题
<div id= "crumb " runat= "server ">
</div>
<div id= "contentDiv ">
<div id= "left ">
<asp:ContentPlaceHolder ID= "ContentPlaceHolder1 " runat= "server ">
</asp:ContentPlaceHolder>
</div>
<div id= "right ">
</div>
</div>
<div id= "footer ">
</div>

CSS:
#footer
{
margin-top:20px;
width:1024px;
font-size:small;
}
为什么firefox 中margin-top:20px; 是从 crumb往下20px 而IE7是从contentDiv往下20px;


[解决办法]
contentDiv 里 后面 加上 <div style= "clear:both "> </div>