Can credit card type be determined solely from the credit card number?
Is this recommended or should we always ask client for the type of credit card they're using?
I Googled about it and found this algorithm: http://cuinl.tripod.com/Tips/o-1.htm , is this reliable?
Yes, the site you mentioned is correct. Many sites, incl. Google Checkout I believe, rely on automatic detection of the card type. It's convenient, makes the UI less cluttered (one less input box) and saves time. Go ahead!