Understanding user agents/browsers

What does "Mozilla Compatible Agent" mean?

[mt_biker]

In trying to determine from my Urchin stats which browsers visitors are using I'm confused by what "Mozilla Compatible Agent" actually means.

While Urchin 5, unfortunately, does not report the entire user agent string (only the version number) my research so far tells me that browsers such as Opera, and even IE may identify themselves as Mozilla Compatible Agents.

Can anyone clarify what is going on and if it's possible to know exactly which browsers my visitors are using based on what Urchin is reporting?

[gregbo]

Generally speaking, Mozilla Compatible indicates to the web server that a browser can be served data that it would render in the way that a Mozilla browser can handle. However, since the HTTP user agent field can be easily faked, one cannot guarantee that the information is true.