Your Web server log can reveal which users visiting your sites are using Windows XP with Service Pack 2 (SP2) installed. When you check the user agent strings you might see entries such as the following:
HTTP_USER_AGENT :Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 1.0.3705)
The "SV1" indicates a system running XP SP2. SV1 stands for Security Version 1. You might wonder why Microsoft decided to add SV1 instead of changing the version number.
In the Microsoft Internet Explorer (IE) team's blog, IE Development Manager Bruce Morgan said that " we know from past experience that changing the version number can have a huge impact on site and application compatibility. We felt that since IE for XPSP2 and WS03SP1 does not have significant changes to page rendering, DHTML, the object model, and the like, the level of impact on the Web of an IE version number change was not justified. So adding 'SV1' seemed \[like\] a reasonable compromise between no changes to the \[user agent\] string and a version number change."
If you wonder whether Microsoft will continue the trend of using SV indicators, the answer is maybe. Morgan added that "\[at\] some point in the future, we’ll want to release the next round of security improvements that are, for example, as far beyond XPSP2 as XPSP2 was beyond XPSP1. If this was part of a release that did change the platform (rendering, DHTML, object model, etc), then we would probably change the version number, otherwise we probably simply change 'SV1' to 'SV2.' We might remove SV1 if we do update the IE version."
If you interested in keeping up with the developments in IE then consider visiting the IE team's blog, which is hosted on the Microsoft Developer Network (MSDN). And if you interested in what was said during a recent online chat with the team then you can read the transcript at Microsoft's site.