The Web Analytics feature in SharePoint 2010 is a great new addition and allows you to get some insights on how your users behave whether it's an Intranet, Extranet or a public facing web site.
One of the reports is called Top Browsers and shows which web browser that the users are using to access the site. For a public facing web site this report might make sense but for an Intranet the results may cause you a headache if you do not understand how to interpret the data.
Let's assume that you have an Intranet with a standardized web browser platform with Internet Explorer 8. If you take a look at the statistics you will first notice that the most used browser is Internet Explorer 7, following that are most often Unknown and/or Netscape4. Internet Explorer 8 is coming later down (together with instances of Safari, Firefox, Chrome etc. - some people just have disobey the corporate rules :-).
So why is Internet Explorer 7 the top used browser then - this is really easy to find out since on intranets IE8 and IE9 uses the Compatibility mode by default, that is it's acting as IE7 and sends that user agent string (see MS-IEDOCO 2.1.2.5). So the Web Analytics treats this session as an IE7 session. The default master page (v4.master) adds the X-UA-Compatible meta header which switches the document mode to IE8 though during runtime.
What about Netscape4 and Unknown then? These requires us to understand a little bit more about how SharePoint is used on an Intranet. An Intranet is not just used by a web browser, people are requesting information using for instance the Office clients (Word, Excel etc.). When the Office clients talks to SharePoint through the WebDAV protocol it sends its own user agent string (for instance: Microsoft Office/14.0 (Windows NT 5.1; Microsoft Outlook 14.0.4734; Pro)). Web Analytics does not "recognize" this one and places it in the Unknown bucket. The Netscape4 browser comes from the same source but are used when detecting which version SharePoint has, when the Front Page Server Extensions requests the _vti_inf.html file.
I hope that this gave you some insights in how the SharePoint 2010 Web Analytics interprets the user agent strings.
