Am I penalised by Google? And how can I find out?

[GeorgeTH]

Looking over the stats of my TGPs I notice that I get twice as much traffic from Yahoo (and some days even more from Altavista) than from Google...

Not that I complain about the Yahoo traffic and hits from Altavista, etc. But I wonder if my site(s) have been penalised by Google - for what I have in the ALT text of my spacer gif...

Last year I'd been with Google for yonks on page 1 results for "free porn" - partly because I used this as the ALT text for my spacer gif (just couldn't think of any better use - no direct intention to spam). Then I was suddenly dropped to somewhere into the 900-1,000 of the "free porn" results. And ever since my Google traffic isn't what it used to be - even for most other terms! I still manage page 1 or 2 results on Yahoo, Altavista, and others, but for the same terms I might be down on page 8-10 with Google...

So how can I find out if I have been penalised - and, if so, how can I change this?