Firefox is clearly on the rise, with some sites seeing as much as a 30% drop in traffic from IE (via gemal.dk). Robin Good’s collection of sites shows Firefox at 20%, Netscape at 8%, IE 6 at under 60%, and older versions of IE chugging along at low levels.

W3Schools shows a slightly more sober 17.5% Firefox, 65.1% IE 6, with IE 5 weighing in at 4.6% to give IE a total market share of just under 70%.

Stats on Hyperborea.org show just 12.6% Firefox and 78.5% IE (73% IE6, 5.5% IE5), with Mozilla taking up most of the slack.

Why the differences? Part of it is different stat collecting methods, but a lot of it has to do with the type of sites being looked at. If web designers are more likely to use Mozilla, you’ll see a higher percentage of Mozilla users on those sites. Technophiles are more likely to be trying out the hot new browser (and today that’s Firefox), so sites they frequent will show that extra percentage.

If you look at the stats for my Flash site (which gets the most traffic), you get 78% IE and 18% Mozilla variants (including Firefox). Katie’s site, which is mostly writing, got 79% IE and only 5.5% Mozilla last month, but my writing site got 64% IE and 11% Mozilla. Stats are even more skewed for K-Squared Ramblings, which has so many pages compared to visitors that 28% of the traffic goes to search engine spiders like Googlebot, Yahoo! Slurp, and Teoma, leaving only 33% for IE and 22% for Mozilla.

So the numbers themselves are essentially meaningless. You can’t look at any site—or piece of a site—and determine that X browser has Y% of the overall market. You only really be sure of the makeup of your audience.

Trends, on the other hand… those can be useful. And just about every stat collecting service I’ve seen says that Firefox is climbing at IE’s expense. The directions are the same, even if the magnitudes are different.

It will be very interesting to see what the web browser market looks like a year from now.