屏蔽鼠标右键 F5 退格键， CTRL+R

<script type="text/javascript">
function  document.oncontextmenu(){event.returnValue=false;}//屏蔽鼠标右键

function  document.onkeydown()
{
  if   ((event.keyCode==8)     ||                                   //屏蔽退格删除键
            (event.keyCode==116)||                                   //屏蔽   F5   刷新键
            (event.ctrlKey   &&   event.keyCode==82)){   //Ctrl   +   R
          event.keyCode=0;
          event.returnValue=false;
          }

}
</script>