If you're going to set up tracking I highly suggest going all the way and using Google Analytics. Unfortunately it's been so popular that they aren't accepting new sign-ups now, but it's worth a mention because the statistics provided are amazing. If you have a shopping cart, it's quite easy to go one step further and have your site send detailed information to Analytics for even better tracking. We recently set this up for a client using osCommerce and the data has been invaluable to them.