直接上代码

<script language="javascript"> 
<!--
function showdiv(){
    if(document.getElementById('Layer_main').style.display!='none'){
        document.getElementById('Layer_main').style.display='none';
    }else{
        document.getElementById('Layer_main').style.display='';
    }
}
-->
</script>
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<div id="Layer_main" style="display:;">
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</div>
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<input type="submit" name="Submit" onclick="showdiv();" value="Go" />