windows vs forms authentication

hi,

We have a requirement wherein we need to authenticate a user from Site A à Site B.

Site A is an intranet site using Window integrated authentication whereas Site B is an internet facing site and using forms based authentication.

In our case Site A is a SharePoint Site and Site B can be anything. When the user in Site A clicks on the link of site B, the system is prompting for a user credentials. We have a dedicated username/password for site B that can be used. We want to use this dedicated user credentials and navigate to Site B without being prompted for a username password validation.

In the above scenario , what options do we have? Any help in this regard will be really appreciated.

Technology Used – SharePoint 2010, XSLT, JavaScript, .Net.