how to add parameters in Internet Sales log-on page?

Hi,

We are using CRM 4.0 for our Internet Sales application (ISA). My question is, how can we add new parameter(s) in log-on page? The standard log-on page parameters are the UserID and Password only, But I need to add new parameter, Is it possible to do so? and How? I tried adding parameters by editing JSP where once I log-on, the log-on JSP will call customized page... In this scenario, session is cut/cleared and I got invalid session. How can I avoid this?

Please help.

Thank you.