The past couple weeks there has been an ongoing debate among many of the prominent warbloggers and some of their media critics over weblog traffic. Unfortunately most of that debate has centered around hits and unique visitors, both of which are completely bogus methods of tracking traffic.
Using hits as a metric has obvious flaws, since every graphic viewed or stylesheet accessed counts as a hit. Two sites with similar levels of hits might have very large differences in the number of people visiting a site.
Unique visitors is also a bogus statistic, though one that is very popular with advertisers and web site operators. The folks who make the free web log analyzer I use, analog, succinctly summarize the problem with unique visitors,
You can’t tell how many visitors you’ve had. You can guess by looking at the number of distinct hosts that have requested things from you. Indeed this is what many programs mean when they report “visitors”. But this is not always a good estimate for three reasons. First, if users get your pages from a local cache server, you will never know about it. Secondly, sometimes many users appear to connect from the same host: either users from the same company or ISP, or users using the same cache server. Finally, sometimes one user appears to connect from many different hosts. AOL now allocates users a different hostname for every request. So if your home page has 10 graphics on, and an AOL user visits it, most programs will count that as 11 different visitors!
The only thing you reliable measure of traffic is page views, and even there the issue of pages cached at ISPs is a problem. Of course page views do not actually tell you a lot.
For example, I know that in May 2002, my web server displayed slightly more than 415,000 page views. I have no idea how many different users that represented and, frankly, I don’t care. Total page views is the best metric to compare relative traffic among web sites.