firefox IE7 布局问题

Question

<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;

Answer 1

不会吧，应该都是footer之上20吧

Answer 2

contentDiv 里 后面 加上<div style="clear:both"></div>

Answer 3

问题解决了clear:both 可以 谢谢