The number of Windows users on the Internet continues to erode as the number of Mac users keeps creeping upward, according to data pulled from Net Applications.

When Net Applications released its monthly traffic report earlier this week, many Web sites dutifully reported that Mac OS X’s share of Web traffic had hit a high of 7.83 percent, with Windows slumping to a new low of 91.13 percent. Data for Apple’s Safari Web browser showed that it, too, hit a high of 6.25 percent in May.

Before continuing I must point out that although Net Applications describes its data as “market share,” a more accurate description would be “user share,” as in the percentage of people on the Web using a particular operating system or Web browser. Market share more accurately describes the percentage of people purchasing a product.

The free monthly statistics Aliso Viejo, Calif.-based Net Applications publishes derive from data the company gathers in the course of its business -- measuring Web traffic for its clients. So while not a scientific sample, it’s broad enough to indicate general trends accurately.

In particular this data excels at revealing long-term trends (Net Applications’ Web site conveniently provides data going back two years), and there we find a good bit of positive news for Apple.

The month-to-month data often obscures these trends. For instance, Mac OS X share hit 7.57 percent in January but dropped to 7.46 percent in February and to 7.38 percent in March.

But look at the two-year operating system charts. Since June of 2006, Mac OS X users on the Web have nearly doubled from 4.29 percent to 7.83 percent while Windows users have declined from 95.25 percent to 91.13 percent. (Toss in the iPhone’s 0.16 percent – the device does run OS X, after all – and Mac OS X’s share climbs to 7.99 percent.)

The lines are crooked but the trend is unmistakable – the Mac is relentlessly taking share from Windows.

Most of Windows’ loss of 4.12 percent went to Mac OS X – 3.54 percent – with Linux (0.30 percent), the iPhone and “Other” accounting for the rest.

Yes, the process is very slow and Windows still holds over a 90 percent share, but the numbers tell us Apple’s strategy is working. The Mac is steadily winning converts.

As for the iPhone, its share grew quickly after last year’s introduction, but has slowed in recent months (it was 0.13 percent in January). Net Applications offers no stats on the iPod Touch (probably too infinitesimal to register).

Should Apple succeed in its stated strategy to evolve those products into a new mobile platform, expect to see that success reflected in Net Applications’ monthly reports.

Apple has also made long-term progress on the browser front. Safari’s share of users has nearly doubled from 3.19 percent two years ago to 6.25 percent. The Mac version of Safari has gotten a little boost in recent months from the Windows version (0.28 percent), but most of the increase has come from the growing Mac user base.

If Safari’s rising share does not yet concern Microsoft, Firefox’s should. In two years Firefox has picked up 7.64 percent, rising from 10.77 percent in June 2006 to a very respectable 18.41 percent in Net Applications’ May report.

Internet Explorer, which had a share of about 95 percent as recently as 2003, saw that dominance fall to 84.11 percent two years ago and another 10.36 percent since, to 73.75 percent.

This tells me we could be on the verge of Browser Wars 2.0, this time with Apple’s Safari participating as a significant combatant.