hi as you know, in webmaster Tools area you can define Geographic target for google. my site users are not in a particular location, ( for example usa). but as you know the USA and Canada and the UK clicks have more rates in ads. i wanna know, does it ok to target my visitors to the USA and Canada and the UK, or it may decrease my visitors from GOOGLE
It all depends in you if you wanna target US and UK. And your traffic would also depends on your rankings and number of links that refer to your site.
I have my web site geographically targeted....my Alexa ranking has gone down because they probably block my site from search results outside the United States. It doesn't matter now that I'm a PR 4 and top of non-sponsored Google SERP for my region and KW. I would rather have ALL my traffic from the United States, because that is where my customers come from. I've also noticed a HUGE DROP in Nigerian Scam E-Mails (people from outside the US, probably in Africa, who want to send me a bogus cashier's check for services), thanks to Geographic Targeting!