Just incase you use google basefeed (google merchant, or google shopping) their new specifications go live tomorrow, sept 22nd 2010.

basically you need to have a brand, a UPC / EAN and a manufacturer part number for everything, and if you sell clothes then you need a google product type and a google product category added to your existing feed.

here is the announcement
(http://googlemerchantblog.blogspot.com/2011/09/upcoming-google-product-search-feed.html)

*Understanding Changes to Product Search UK: http://www.youtube.com/user/GoogleECommerce#p/u/1/RICDQm29iUw
*Providing High-Quality Data: http://www.youtube.com/user/GoogleECommerce#p/u/4/FrW5BrMqziA
*Troubleshooting Tools: http://www.youtube.com/user/GoogleECommerce#p/u/3/f8KoiuKnl00

this is what they will do to you if you dont
http://www.google.com/support/merchants/bin/answer.py?answer=188484.

full spec is available at
http://www.google.com/support/merchants/bin/answer.py?answer=188494&expand=GB.

there is also a ‘submit test feed’ option in the merchants dashboard > data feeds
you can upload a file and google will check that it works and has all the required attributes and will even give you a csv with the errors in it.