Hi,
To integrate Payment gateway of ICICI or HDFC bank, you must have an merchant account. The details are sent to you after you get your account. You simply have to change the parameters & customize the code as sent to you from the bank.
Normally HDFC bank payment gateway cost rs.1 Lakh & i think it will be similar for ICICI bank (May be less), but u have to provide complete proofs of valid business, An current account with the bank on the name of business u r running,,,,,,blah....2. lots of fomalities....finally u get the code n simply modify..n enjoy..