屏蔽浏览器关闭按钮及ALT+F4 快捷键

屏蔽Alt+F4等快捷键：
<script>
functionKeyDown(){//屏蔽鼠标右键、Ctrl+n、shift+F10、F5刷新、退格键
//alert("ASCII代码是："+event.keyCode);
if((window.event.altKey)&&
((window.event.keyCode==37)||//屏蔽Alt+方向键←
(window.event.keyCode==39))){//屏蔽Alt+方向键→
alert("不准你使用ALT+方向键前进或后退网页！");
event.returnValue=false;
}
if((event.keyCode==8)||//屏蔽退格删除键
(event.keyCode==116)||//屏蔽F5刷新键
(event.keyCode==112)||//屏蔽F1刷新键
(event.ctrlKey&&event.keyCode==82)){//Ctrl+R
event.keyCode=0;
event.returnValue=false;
}
if((event.ctrlKey)&&(event.keyCode==78))//屏蔽Ctrl+n
event.returnValue=false;
if((event.shiftKey)&&(event.keyCode==121))//屏蔽shift+F10
event.returnValue=false;
if(window.event.srcElement.tagName=="A"&&window.event.shiftKey)
window.event.returnValue=false;//屏蔽shift加鼠标左键新开一网页
if((window.event.altKey)&&(window.event.keyCode==115)){//屏蔽Alt+F4
window.showModelessDialog("about:blank","","dialogWidth:1px;dialogheight:1px");
returnfalse;}
}
functionShowhelp(){
alert("Wrong!");
returnfalse;
}
</script>