http://www.artlebedev.com/tools/browsers/
What They Count
Hits on Russian-language banner adverts.
Measuring period and update frequency
Daily, no history.
Browser Detection
Not that good. The headline figures are IE/"Netscape"/Other, with IE broken down by major version, and "Nescape" split by major version with a separate "Mozilla" category.
Demographics
The link to Russian-language content will obviously have an effect. Less obvious is the fact that it will only "see" users who visit sites which carry banners.
The stats can wobble quite a bit from day to day. I think this is mostly a day-of-the-week demographic effect, but there's probably a healthy dose of random noise in there, too. Sample size seems to be ~3m banners/day at the weekends, ~5-6m during the week
[last updated: 2005-04-23]
[This is one of an irregular series of posts detailing sources of free web browser statistics. It is back-dated into the prehistory of the web to allow easy access to the entire series]