web server logs are totally unreliable. For years it's been not only
possible, but required for some sites, to report your system as wrong. Back in the days of MSIE 6 a lot of web sites were optimised for MSIE and if your system reported itself as using anything but MSIE on Windows to the server you had some sort of issues with the site, but fudge the outgoing info to tell the server your Linux install with Fire Fox was Windows with MSIE and the site worked OK. I never did get a handle on how or why it happened, but I did have several sites I went to where making that change in reporting made a difference to how you could see and use the site. That was still the case in MSIE 7 and I don't know about with MSIE 8 or since as I gave up on that before MSIE 8 came out and just set the system NOT to report what the system was. Today, I don't give a damn either way.