Error on Firefox not found in Safari

[Penn]

On my mac, I am running

Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-US; rv:1.8.1.7) Gecko/
20070914 Firefox/2.0.0.7

and

Safari Version 3.0.3 (522.12.1)

My gadget:

http://www.powderdrop.com/powderdroptest.xml

runs very well on Safari, but not on Firefox. I get a bad URL
report. Is there anyway to run the gadgets in some type of debug
mode? Any ideas on why this runs on one and not the other?

Thank you!!!

http://validator.w3.org/check?uri=http://www.powderdrop.com/powderdroptest.xml