js禁止页面刷新后退

1. <script    language="javascript">       
   //禁止用F5键       
   function    document.onkeydown()       
   {       
             if    (    event.keyCode==116)       
              {       
                      event.keyCode    =    0;       
                      event.cancelBubble    =   true;       
                     return   false;       
              }       
   }       
           
   //禁止右键弹出菜单       
   function    document.oncontextmenu()       
   {       
         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>   
   <script language="Javascript"><!--    
   //屏蔽鼠标右键、Ctrl+N、Shift+F10、F11、F5刷新、退格键    
   //Author: meizz(梅花雨) 2002-6-18    
   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;    
   }    
   /* 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;    
   }    
   }    
   </script>