屏蔽键盘

<script language="Javascript"> 
//屏蔽鼠标右键、Ctrl+N、Shift+F10、F5刷新、退格键
//屏蔽F1帮助
function window.onhelp() 
{ 
return false 
} 
function KeyDown() 
{ 
//alert(event.keyCode); 
//屏蔽Alt+ 方向键←屏蔽Alt+ 方向键→
if ((window.event.altKey)&&((window.event.keyCode==37)||(window.event.keyCode==39))) 
{ 
//alert("不准你使用ALT+方向键前进或后退网页！"); 
event.returnValue=false; 
} 
//屏蔽退格删除键,屏蔽F5 刷新键,Ctrl + R 
if ((event.keyCode==116)||(event.ctrlKey && event.keyCode==82)) 
{ 
event.keyCode=0; 
event.returnValue=false; 
} 

//屏蔽Ctrl+n 
if ((event.ctrlKey)&&(event.keyCode==78)) 
{ 
event.returnValue=false; 
} 

//屏蔽shift+F10 
if ((event.shiftKey)&&(event.keyCode==121)) 
{ 
event.returnValue=false; 
} 

//屏蔽shift 加鼠标左键新开一网页
if (window.event.srcElement.tagName == "A" && window.event.shiftKey) 
{ 
window.event.returnValue = false; 
} 

//屏蔽Alt+F4 
if ((window.event.altKey)&&(window.event.keyCode==115)) 
{ 
window.showModelessDialog("about:blank","","dialogWidth:1px;dialogheight:1px"); 
return false; 
} 

//屏蔽Ctrl+A 
if((event.ctrlKey)&&(event.keyCode==65)) 
{ 
return false; 
} 
return false;
} 
document.onkeydown=KeyDown;
</script>