屏蔽 F5 刷新键

<script language="JavaScript" type="text/javascript">
document.onkeydown = function(){
 var k = window.event.keyCode;
 if (k == 116){ //屏蔽 F5 刷新键
 window.event.keyCode = 0;
 window.event.returnValue= false;
 }
}
</script>