Reverse engineering HTTP transactions

[Joost]

I am trying to log in to a site and get a page for some parsing, but I can't seem to mimic everything they are doing in the login (so it doesn't work).

I've had the same problem a few times, and the easiest to use tool I found to track down the data exchanged is lynx - the text-only browser. You can put it in trace-mode and examine all traffic to and from the server. This will probably give you some insight in what's going on (i.e: get/post data, cookies, redirects etc.)

See also:

http://lynx.browser.org/
man lynx

-- 
Joost       downtime n. The period during which a system
            is error-free and immune from user input.