js禁止页面刷新后退

[javascript]
<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

补充：web前端 , JavaScript ,