js 屏蔽右键

function clickIE4()
 {
  if (event.button==2){  
   return false;
  } 
 }function clickNS4(e)
 {
  if (document.layers||document.getElementById&&!document.all)
  {
   if (e.which==2||e.which==3){
   return false;
   }
  }
 } 
if (document.layers){
 document.captureEvents(Event.MOUSEDOWN);
 document.οnmοusedοwn=clickNS4;
 }
 else if (document.all&&!document.getElementById){ 
 document.οnmοusedοwn=clickIE4;
 }document.οncοntextmenu=new Function("return false");
// disable the BackSpace(8), ALT+Left(37),  ALT+Right(39),  ALT+HOME(36), Enter (13), N(78), n(110)
var ALREADY_CHECKED = false;
 function KeyIE4()
 {
  if(event != null){ 
   var oSource = event.srcElement;
   if (ALREADY_CHECKED) {
    if ((oSource != null && (oSource.type=="text" || oSource.type=="textarea")) && ("8" == event.keyCode || "35" == event.keyCode || "36" == event.keyCode || "37" == event.keyCode || "39" == event.keyCode || "46" == event.keyCode || (event.ctrlKey && "88" == event.keyCode))) { 
     return true;
    } else {
     return false;
    }
   } else { 
    if("8" == event.keyCode && (oSource ==null || (oSource != null && oSource.type!="text" && oSource.type!="textarea"))){
     return false;
    } else if(event.altKey && ("36" == event.keyCode || "37" == event.keyCode || "39" == event.keyCode)){
     return false;
    }else if(event.ctrlKey && ("78" == event.keyCode || "110" == event.keyCode)){
     return false;  // Ctrl + N, restrict for now
    }else if("13" == event.keyCode && (oSource ==null || (oSource != null && oSource.type!="textarea"))){
     return false;
    }else{  
     return true;
    }
   }
  }
 }document.onkeydown = KeyIE4; 
 document.onkeyup = KeyIE4;