Microsoft's share of the browser market across all versions of Internet Explorer has dropped, byone estimate, dropped from 78.58%  in December 2007 to 68.15% in December 2008 (or by just under 8% in another estimate).

[IE's] share dropped from 69.77% in November to 68.15% in December. [During the same period,] Firefox gained more than half a point and ended up at 21.34%, Safari approaches the [10%] hurdle with 7.93% and Chrome came in at 1.04%, the first time Google was able to cross the 1% mark.

This is particularly interesting: 

Since IE6 is used primarily within corporations, its market share is much higher during the week than it is on weekends. As a result, all other browsers gain on weekends and especially during a holiday. Because of that circumstance, Net Applications noted that the December numbers should be taken with a grain of salt. However, it is worth the note that IE6 achieved ... market share numbers of about 28% during the week and about 21% on weekends in early 2008. In December, these numbers were down to about 20% during the week and 15% on weekends.    

So, Microsoft still has an established base among corporate users, where IT administrators  generally prevent employees from installing new applications (including browsers) and the sysadmins often don't roll out alternative browsers across a corporate network for any one of several possible reasons, including:

• They just don't want to bother having to install, regularly upgrade and support another piece of software;
• They may overestimate the security vulnerability of such alternative browsers compared to Internet Explorer;
• The crustier sysadmins may not realize that today's browsers are not only free for individual users, but also for corporate users--unlike the old Netscape Navigator; and
• Corporate intranets may be designed for IE, in which case rolling out an alternative browser might cause confusion among less tech-savvy employees.

Microsoft may still have an advantage that could be considered "unfair," but so what?