障蔽IE浏览器中的功能键

<script>
document.onhelp = function(){window.event.returnValue=false;}
document.onkeydown=noway;           //绑定窗体加载事件
function  noway(){
	if(window.event.keyCode   ==   113)   { 
		alert("dddd");
	} 
	if(window.event.keyCode   ==   114)   { 
		window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   115)   { 
		window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   116)   { 
		window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   117)   { 
		window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   118)   { 
		window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   119)   { 
		window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   120)   { 
	  window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   121)   { 
	  window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   122)   { 
	  window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   123)   { 
	  window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   13)   { 
	  window.event.keyCode   =   505; 
	} 
	if(window.event.keyCode   ==   8)   { 
	  window.event.returnValue=false; 
	} 
	if(window.event.keyCode   ==   505){ 
		window.event.returnValue=false; 
	} 
}
</script>