"Auto Login?" not prompting for new site

I set up a second email account at Yahoo.  I would like "Auto Login?" to prompt me so Norton will save my ID and password and  automatically sign me in from now on.  But when I go to yahoo.com and "sign in", the "Auto Login?" message doesn't come up at the sign in page and I have to type it in manually.  I never had this problem before; usually this process is trouble-free.  I have Norton Internet Security 2010 on Win XP.  Any ideas?