How do you know which keywords are sending traffic?
 

I'm getting some hits from SE but the keywords are not revealed.

Acording to startcounter keywords ranked 2,3 and 10 on google but are unavailable.
The only hit I got from bing revealed the keyword.

Is there a way to have access to that info?.

Webmaster tools will shows search queries and amount of clicks, plus loads of other juicy info.

Google Analytics is your friend.

Google Analytics is covering more than 85% of keywords on our sites, making it less than 15% keywords visible. They are encoding most of the URLs which are showing Google results (HTTP referer), so they don't contain keywords anymore, meaning you can't track them. You can track the same amount of keywords (if not more) using any other web stats that's using Apache logs.

I heard Bing was using the same thing...

Set up analytics, and then there's a button to integrate webmaster tools so that it pulls that data in automatically. It's not perfect, but it helps.

You're also better off downloading your webmaster tools keyword data every 90 days, because they don't save it forever.

If you're getting referral traffic from other sites, it's also important to use the google "url builder" tool to tag your different sources. That way, you know exactly whether a particular banner ad, text link, or whatever is working to drive traffic.

BTW, don't forget to set up goals in google analytics. You want to know what traffic is converting... not just where it's all coming from.

Google Conversion XL (I can't post links since I just joined.) That blog has more info than you'd care to know about all this stuff.