Apparently, it's getting these stats via trackers on Websidestory sites: 31 million pageviews is a decent base for testing, so they cannot be too far off.
Yet again we ask ourselves: "Will Netscape 5 ever arrive? and will it match IE5?" Mozilla might be a wonderful concept, but until Netscape 5 is released for download to everyday users, available on magazine coverdisks and handed out on ISP welcome CDs, Mozilla will hardly effect the stats.
In many ways, Netscape 4 is a perfectly decent browser, but mindshare effects marketshare, and with Netscape/AOL not having released a significant browser in a long time, people will really start to notice and think of them as stale and incompetent.
On the other hand, as workers of the web, we'll still have to design cross-browser Web sites regardless. There will always be enough users of Netscape, Neoplanet, Opera, etc, to warrant designing for everyone. 50%, 75%, 87%? It's not really going to matter who has what percentage of the market - as long as there are at least 5% or so "others" out there, we will be forever on our toes...