For compatibility with IE8 and older use .cancelBubble if .stopPropogation() is undefined:
if(ev.stopPropagation)ev.stopPropagation();
else ev.cancelBubble=true; // where ev is an event object
Read about in MSDN: http://msdn.microsoft.com/en-us/library/ff975961%28v=vs.85%29.aspx