Here's the code for disabling right click in all browsers you need... Put this code within script tags in head

function disableClick(evnt)
{
	if(document.all)
	{
		alert("Sorry... Right click is not allowed.");
		return false;
	}
	if(navigator.appName=="Netscape")
	{
		if(evnt.which==3)
		{
			alert("Sorry... Right click is not allowed.");
			return false;
		}
	}
}
document.oncontextmenu = disableClick;
if(!document.all && document.getElementById)
	document.onclick = disableClick;
if(document.layers)
{
	document.captureEvents(Event.MOUSEDOWN);
	document.onmousedown = disableClick;
}

See this faq (click here). But I guess it doesn't work for Netscape 4.7x etc... Couldn't find any alternative either. Will post if i come across any