This is only the second website I have come across where KWallet does not work; the first one in fact changed its behaviour some months ago so that KWallet does work. It appears the first one created a new portal every week I logged on; so I could log on for about a week and then had to re-enter the user and password. Now it uses the same portal all the time.

Why doesn't this website allow KWallet to work?

Didn't notice that, as i am always logged in (cookie based). In fact the login credentials get saved to the wallet, but the login form is ajax based and gets autofilled with standards. I will look into that. But it is not a KWallet problem, so i am moving this thread.
Thanks for reporting.