Weird log entries

I've been trawling through my web logs and found that a relatively high number of 404 http errors are being generated.

They seem to be caused by someone (or crawler) trying to access pages named after countries. There's a list of about 300 countries.

I guess these are likely to come from a list of values from a frop down box in a form. But the site has no form! So where are these coming from? I jsut dont get it?

Im concerned that this is affecting SERPS and/or PR. Can this have an effect?

I hope someone out there can help?

Rgds
Aj.