As we discuss metrics, I would be remiss if I didn't point out that visitors are one of the easiest metrics to accidentally make a mess of. Here are some of the things that can throw off your visitor metrics:

• Your employees have your web site set as the start page when they open a new browser window

• Your HR department posted a job on Craigslist so potential hires are checking you out

• Your webmaster is updating the site and reloading again and again.

All of these will create spikes in your traffic and skew your numbers.

Some of them can be addressed with the Google Analytics module by turning off tracking of registered users or admins, but it's nearly impossible to remove all the skewed numbers. Don't rely on the absolute numbers—look for trends in the number of visitors.