JS禁止快捷键

    <script language="Javascript">  
    //禁止右键弹出菜单  
    function   document.oncontextmenu() {        
          return   false;        
    } 
    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;      
        }      
        /* 注：这还不是真正地屏蔽 Alt+ 方向键，    
        因为 Alt+ 方向键弹出警告框时，按住 Alt 键不放，    
        用鼠标点掉警告框，这种屏蔽方法就失效了。以后若    
        有哪位高手有真正屏蔽 Alt 键的方法，请告知。*/      
        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;      
        }      
    } 
    //下面代码实现全屏显示        
    function   window.onload(){        
        var Request = new Array();//保存参数        
        var s = location.search.substring(1);        
        if (s && s!=""){        
            var list = s.split("&");        
           for (var  i=0; i < list.length; i++){        
               var pair = list[i].split("=");        
               if(pair[0] && pair[0] !=""){        
                  Request[unescape(pair[0])] = unescape(pair[1]);        
               }        
           }        
        }      
        var  fullscreen=Request["fullscreen"];        
        if(fullscreen!="yes"){        
            var  file = self.location;        
            var a = window.open("about:blank","","fullscreen=yes")        
            self.opener=null        
            self.close()        
            a.location=file + "?fullscreen=yes";        
        }        
    } 
    </script>