Tweaked the default Accept header to _default.

src/ajax.js

@@ -153,7 +153,7 @@ jQuery.extend({
 			script: "text/javascript, application/javascript",
 			json: "application/json, text/javascript",
 			text: "text/plain",
-			"default": "*/*"
+			_default: "*/*"
 		}
 	},