网页屏蔽各种按键的代码分享

<script> 
//屏蔽鼠标右键、Ctrl+N、Shift+F10、F11、F5刷新、退格键 
function document.oncontextmenu(){event.returnValue=false;}//屏蔽鼠标右键 
function window.onhelp(){return false} //屏蔽F1帮助 
function document.onkeydown(){ 
 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.ctrlKey && event.keyCode==82)){ //Ctrl+R 
 event.keyCode=0; 
 event.returnValue=false; 
 } 
 if(event.keyCode==122){event.keyCode=0;event.returnValue=false;} //屏蔽F11 
 if(event.ctrlKey && event.keyCode==78)event.returnValue=false; //屏蔽Ctrl+n 
 if(event.shiftKey && event.keyCode==121)event.returnValue=false; //屏蔽shift+F10 
 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"); 
 return false; 
 } 
if(window.event && window.event.keyCode == 123) {
  alert("F12被禁用");
  event.keyCode=0;
  event.returnValue=false;
 }
 if(window.event && window.event.keyCode == 13) {
  window.event.keyCode = 505;
 }
 if(window.event && window.event.keyCode == 8) {
  alert(str+"\n请使用Del键进行字符的删除操作！");
  window.event.returnValue=false;
 }
 } 
</script>