How to determine users mobile tel company?

[waynemac]

Greetings all, I run a forum and information website in Japan.

I am setting up a mobile site that is accessed by 3 different mobile phone companies (docomo, skyweb and ezweb).

I want to determine where the incoming visitors from so to dish up different pict files as some use png and not gif and vis-a-versa. The common pict file type is jpeg and thats too big for what Im doing.

Ive looked around but cant find what Im looking for.

AND, from there, how would I encode it to pull different file types? Is there an "if this browser then access image folder A, if not then B" script?

Im new to this so any input would be appreciated.

Thanx in advance, Wayne in Japan

[sciguyryan]

You can get which site refered a user using the document.referrer but, it is not reccomended because its easily fooled and ins ome browsers it is not dispalyed or can be altered.

RyanJ