屏蔽快捷鍵

//屏蔽鼠標右鍵     
 function document.oncontextmenu()     
 {     
     event.returnValue=false;     
 }     
 //屏蔽F1幫助     
 function window.onhelp()                       
 {     
     return false;     
 }     
 //屏蔽其他功能鍵  
 function document.onkeydown()     
 {     
     var k = window.event.keyCode;
     if(k == 116)//屏蔽 F5 刷新鍵                                            
     {     
           window.event.keyCode  =  0;     
           window.event.returnValue =  false;     
     }     
      
     if(window.event.ctrlKey && k == 82)//Ctrl + R     
             window.event.returnValue=   false;     
     if(window.event.ctrlKey && k == 78)//屏蔽Ctrl+n     
            window.event.returnValue =  false;     
     if(window.event.ctrlKey && k == 87)//屏蔽Ctrl+w     
             window.event.returnValue =  false;     
     if(event.shiftKey && k==121)//屏蔽 shift+F10     
             window.event.returnValue = false;     
     if(window.event.srcElement.tagName == "A" && window.event.shiftKey)       
             window.event.returnValue  =  false;//屏蔽 shift 加鼠標左鍵新開一網頁     
     if(window.event.altKey && k == 115)//屏蔽Alt+F4     
     {    
          window.showModelessDialog("about:blank","","dialogWidth:1px;dialogheight:1px");   
           return   false;     
     }    
     if(window.event.altKey && window.event.ctrlKey && k == 110)
       window.event.returnValue  =  false;
     if(window.event.altKey &&
           (k == 37   || //屏蔽 Alt+方向鍵 ←     
             k == 39)) //屏蔽 Alt+ 方向鍵→     
     {     
          alert("不准你使用ALT+方向鍵前進或後退網頁！");     
          event.returnValue=false;     
     } 
  }