//Identify if user is using IE4
    var agt=navigator.userAgent.toLowerCase(); 
    var is_major = parseInt(navigator.appVersion); 
    var is_minor = parseFloat(navigator.appVersion);     var is_ie   = (agt.indexOf("msie") != -1); 
    var is_ie4  = (is_ie && (is_major == 4) && (agt.indexOf("msie 5.")==-1) ); 

 //Disable right-click menu
if (navigator.appName == "Netscape")
{
	if (navigator.appVersion.indexOf('5.0') != -1)
	{
	document.onmouseup = 
	   function (evt) {
	    if (evt.button == 3)
	    evt.preventDefault();
	    }
	}
	else {
	document.captureEvents(Event.MOUSEDOWN);
	document.onmousedown = 
	function (evt) {
	    if (evt.which == 3)
	     return false;
	   };
	}
}
else { 
if (is_ie4) { document.onmousedown = function () { if (event.button!=1) {  alert("This option is not available.");event.returnValue=false;} } }
else { document.oncontextmenu = function () { return false; } }
}