<script language="javascript"> 
<!-- 
function document.onkeydown() 
{ 
if ((event.keyCode==116)|| event.ctrlKey)      //屏蔽 F5 键和ctrl键 
{
alert("已经屏蔽F5和CTRL键!"); 
event.keyCode=0; 
event.returnValue=false; 
} 
} 
--> 
</script>