M$ user agents strings and the others

Source (modified)

What did this study conclude?

• First, lots of users are not running the most up-to-date and secure versions of their Web browsers.
• Second, this is primarily a phenomenon of Internet Explorer users;

Firefox users, on the other hand, overwhelmingly update their browsers quickly.
These and other results led the authors to suggest that browsers get expiration dates, much like milk and pharmaceuticals.
It's fair to assume that the test sample is a highly representative one, as Google is both dominant in the search business and used worldwide. I could argue that users of Microsoft's search engine are more likely to use Internet Explorer than are Google users, but this is a small, marginal difference. The problem is not in the users, but in the user-agent string.

The user agent is a string that a browser, or "user agent" (the more general programming term for Web clients), presents to a Web server as part of a request.

Click here to see your own browser's user agent.

Click here to see a database of different user agents for different browsers and other "user agents." Servers log this data and often use it to determine which content to send to the client.
I always run both Firefox and IE7. Currently my Firefox user agent is:

Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0

and my ie7 user agent is:

Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506; InfoPath.2; MS-RTC LM 8)

You can see pretty easily that the Firefox one is Firefox 3.0, that it's running on Vista set for U.S. English. 1.9 is the version of the Gecko engine and "2008052906" is the build data for that engine. In the IE7 string, we can also see that it's Vista. The "SLCC1" is not clear but may refer to security licensing components. You get versions for .NET CLR and Media Center. I don't know what "MS-RTC LM 8" is. [Update: Thanks to a reader at Microsoft for pointing out that "MS-RTC LM 8" refers to Live Meeting 2007.]

But note that the build data and Gecko version on Firefox give you a lot more version information about Firefox than you get about Internet Explorer. For IE, all you get is major version information, i.e. IE5, IE6, IE7, IE8. The study authors note this themselves:
The USER-AGENT header fields for Firefox, Safari, and Opera contain both major and minor version information, whereas Internet Explorer only contains the major version. Therefore, it was not possible to enumerate the patch level of Microsoft Internet Explorer using this method beyond its major release numbers.
After Clicking here I can see my own browser's user agent (in this case flock1.2)

Your User Agent String:
Mozilla/5.0 (Windows; U; Windows NT 5.1; es-ES; rv:1.8.1.16) Gecko/20080831 Firefox/2.0.0.16 Flock/1.2.5

Flock 1.2.5
Mozilla	It's a Mozilla based browser
5.0	Mozilla Version
Windows	Platform
U	Security values: N for no security U for strong security I for weak security
Windows NT 5.1	OS-or-CPU : Windows XP
es-ES	Language Tag, indicates the language for which the client had been localized (e.g. menus and buttons in the user interface) :
rv:1.8.1.16	CVS Branch Tag The version of Gecko being used in the browser
Gecko	Gecko engine inside
20080831	Build Date: the date the browser was built
Firefox	Based on Firefox
2.0.0.16	Firefox version
Flock	Flock
1.2.5	Version