急救！！！怎么样让 表头覆盖select


       <html> 
<head> 
<meta   http-equiv="Content-Type"   content="text/html;   charset=gb2312"> 
<title>JK:支持民族工业,尽量少买X货</title> 
<style> 
.fixedHeaderTr    
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position:relative;    
top:expression(this.offsetParent.scrollTop);    
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overflow:auto;    
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width:expression(document.body.clientWidth-20);    
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</style> 
</head> 
   
    <body>       <div   class="mainDiv"> 
            <table   width="100%"   border=1   cellspacing=0   style="margin-top:-2px"   > 
            <TR   class="fixedHeaderTr"   bgcolor="red" > 
            <TD   >Header   A</TD> 
            <TD   >Header   B</TD> 
            <TD   >Header   C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD> 
                C部分代码来自：<br/> 
                http://blog.csdn.net/wu_yongcai/archive/2004/11/21/189816.aspx</TD> 
            </TR> 
            <TR> 
            <TD><select name="fdkc"   onchange="fdkcchange()" size="1" style="width:100%;height:100%"  onkeydown="if(event.keyCode==13)event.keyCode='9'" />
                              </select></TD> 
            <TD><select name="fdkc"   onchange="fdkcchange()" size="1" style="width:100%;height:100%"  onkeydown="if(event.keyCode==13)event.keyCode='9'" /></TD> 
            <TD><select name="fdkc"   onchange="fdkcchange()" size="1" style="width:100%;height:100%"  onkeydown="if(event.keyCode==13)event.keyCode='9'" /></TD> 
            </TR> 
            <TR> 
            <TD><select name="fdkc"   onchange="fdkcchange()" size="1" style="width:100%;height:100%"  onkeydown="if(event.keyCode==13)event.keyCode='9'" /></TD> 
            <TD><select name="fdkc"   onchange="fdkcchange()" size="1" style="width:100%;height:100%"  onkeydown="if(event.keyCode==13)event.keyCode='9'" /></TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD><select name="fdkc"   onchange="fdkcchange()" size="1" style="width:100%;height:100%"  onkeydown="if(event.keyCode==13)event.keyCode='9'" /></TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD><select name="fdkc"   onchange="fdkcchange()" size="1" style="width:100%;height:100%"  onkeydown="if(event.keyCode==13)event.keyCode='9'" /></TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD><select name="fdkc"   onchange="fdkcchange()" size="1" style="width:100%;height:100%"  onkeydown="if(event.keyCode==13)event.keyCode='9'" /></TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD><select name="fdkc"   onchange="fdkcchange()" size="1" style="width:100%;height:100%"  onkeydown="if(event.keyCode==13)event.keyCode='9'" /></TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
           
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            <TR> 
            <TD>A</TD> 
            <TD>B</TD> 
            <TD>C</TD> 
            </TR> 
            </table> 
      </div> 
    </body> 
</html>
我用的是IE6.0 这面代码可以 看到错误 表头让select 覆盖了 怎么解决啊 谢谢大家了