Some time ago, I performed a “test to determine when MSIE is not MSIE”:http://virtuelvis.com/archives/2003/02/properly-measuring-msie, and I just retested with numbers from March 2003.
The short version is this:
Through the User-Agent string, 58.9% of my visitors *claim* to be using MSIE, while only 38.1% of my visitors are fetching the MSIE-specific stylesheet included with conditional comments.
35.2% of browsers that claim to be MSIE aren’t. 84.2% of browsers that use a faked MSIE UA string, are using Opera. Opera’s “real” market share among CSS-capable browsers is 45.3%.
*Update:* Disclaimer: Although, I use the phrase “market share”, it should not in any way be confused with a _general_ market share for browsers. The literal figures are valid only in the context of the sampled site. The point is the overrepresentation. This is also explained in the “previous article on the same subject”:http://virtuelvis.com/archives/2003/02/properly-measuring-msie.