I have suspected that Google Analytics hides things it doesn't understand for a few weeks now. Whilst I am not certain about that, it definitely misses some things, and gets others wrong. Let us examine what it misses first. Some old browsers register only the first page visited, and the rest are not counted. This results in Google Analytics marking their visits as "bounces," when these visitors did, in fact, view multiple pages. For example, Mozilla 4 and lower appear to cause this. Other browsers do not even register at all, resulting in uncounted visits. These details were obtained by comparing the results from Google Analytics, to this site's server logs.