You can change user agent in firefox by going to
about:config
Then add a new “String” by right clicking.
Give “general.useragent.override” as name of the string.
For the value, use what you need.
I put
Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
So when you visit web site, access log will have it like
59.98.40.114 s1.video.bizhat.com - [22/Aug/2008:21:41:00 +0000] “GET /up.html HTTP/1.1″ 200 3 “-” “Mozilla/5.0 [...]