Single Signon DIV onLogon Need Not Refresh the Entire Page

Single Signon DIV onLogon Need Not Refresh the Entire Page

I just thought that when you logon using the Single Signon DIV, the entire page refreshing is unwarranted. Only that DIV and the span which indicates Log Out [username] needs to be repainted right?

I understand that there may be hidden fields and cookies to be set. Can't these be set on response from an AJAX JavaScript Call?