禁止浏览器右键菜单弹出

<script type="text/javascript">
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;
            }
        }
}
function OnDeny()
{
       if(event.ctrlKey || event.keyCode==78 && event.ctrlKey || event.altKey || event.altKey && event.keyCode==115)
       {
          return false;
       }
}
if(document.layers)
{
tureEvents(Event.MOUSEDOWN);
        document.onmousedown=clickNS4;
        document.onkeydown=OnDeny();
}
else if(document.all&&!document.getElementById)
{
        document.onmousedown=clickIE4;
        document.onkeydown=OnDeny();
}
document.oncontextmenu=new Function("return false");
</script>