From Linuxintro

firefox extended settings

You can find all firefox settings if you surf to about:config

masquerading as Internet Explorer

Browsers identify themselves when they request web pages. Some web pages will only work if the browser states it is an Internet Explorer. To make your FireFox pretend it is an InterNet Explorer, surf to about:config and add a key/value pair

general.useragent.override = Mozilla/4.0 (compatible; MSIE 5.5; Windows 98)

You can find out the information transmitted by your browser to the web server using netcat. Open a console and start netcat listening on port 80 on your local computer:

# netcat -l -p 80

Then start firefox, disable any Proxy (select Edit -> Preferences -> Advanced -> Network -> Settings -> No proxy) and surf to http://localhost. You will see some output on your console like this:

GET / HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20110920 SUSE/3.6.23-0.2.1 Firefox/3.6.23
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 115
Connection: keep-alive

This is how firefox talks with a web server!

See also