On my kindle’s browser, an azure hosted web forms project offering a google (websso) login didn’t work. It became quickly apparent that the forms auth cookie presented back to the site was invalid in some way (or perhaps not present!); meaning that SP site would loop back to the IDP. If the IDP was set for auto-logon (perhaps the second time one visits…), one gets an endless of loop of websso requests and responses.
Of course, I just happen to be using ASP.NET 4.0 on DotNet 4.0 (so one can use WIF libraries easily, with websso). This turns out to be a nasty combo…till you fix it thus: