Alex,
Personal/Anecdotal Experience
- CSS make little difference
- Large and complex CSS are better to be external
- Internal CSS increase the amount of code in our page and may "push" your "content" down the page out of the spiders reach.(dependent on spider of course)
- I believe Google is aware of spam-CSS tricks.. - but wether they are dealing with it(as Bill said) is another question.
No conclusive warnings or negatives
I will try to find a more specific answer
DD