- var modRes = xml.getResponseHeader("Last-Modified");
- if ( ifModified && modRes ) jQuery.lastModified[url] = modRes;
+ var modRes;
+ try {
+ modRes = xml.getResponseHeader("Last-Modified");
+ } catch(e) {} // swallow exception thrown by FF if header is not available
+
+ if ( ifModified && modRes )
+ jQuery.lastModified[url] = modRes;