这个是什么意思啊?

<script language="JavaScript">
<!--
passwd="ItIsSoEasy";
function disable_right_click(e) {
var browser = navigator.appName.substring ( 0, 9 );
var event_number = 0;
if (browser=="Microsoft")
event_number = event.button;
else
event_number = e.which;
if ( event_number==2 || event_number==3 || event_number==4) {
alert ("这个应该难不倒你吧!");
return (false);
}
return (true);
}
function check_mousekey () {
var mouse_key = 93;
var keycode = event.keyCode;
if ( keycode == mouse_key )
alert ( "这个应该难不倒你吧!" );
}
function trap_page_mouse_key_events () {
var browser = navigator.appName.substring ( 0, 9 );
document.onmousedown = disable_right_click;
if ( browser == "Microsoft" )
document.onkeydown = check_mousekey;
else
document.captureEvents( Event.MOUSEDOWN );
}
window.onload = trap_page_mouse_key_events;
//-->
</script>

屏蔽鼠标按键的代码