<script>
document.onkeydown=function(){if(event.ctrlKey&&(event.keyCode==78)){event.keyCode=0;event.returnValue=false;}}
</script>
<body>
<a href="#1">aaa</a>
</body>
document.onkeydown=function(){if(event.ctrlKey&&(event.keyCode==78)){event.keyCode=0;event.returnValue=false;}}
</script>
<body>
<a href="#1">aaa</a>
</body>
{
if (window.event.ctrlKey && window.event.keyCode == 78)
window.event.returnValue= false;
}