- var data = !type && ct && ct.indexOf("xml") >= 0;
- data = type == "xml" || data ? r.responseXML : r.responseText;
+ var xml = type == "xml" || !type && ct && ct.indexOf("xml") >= 0;
+ data = xml ? r.responseXML : r.responseText;
+
+ if ( xml && data.documentElement.tagName == "parsererror" )
+ throw "parsererror";