Parameters that Determine if there's a Logged In User or Not on the Web Store

To verify if there is a logged-in user or not:

1. Visit the site then click Login link to go to the login page.
2. View source code from the login page. Look at the comment around line 13

<!-- v=2012.2.0.90 db=115 c=TSTDRV329799 n=2 rg=1 e=0 r=17 ct=WEBSITE isstore=T https=T id= cat= sc=8 sct=HOME thm=153 cart=-1 (serno=1) price=5 cur=1 lang=en_US partner=0 promocode=0 leadsource= sobcform=88 sco=F page(candbc=F fromdbc=F vol=F) -->

take note of e=0 and r=17 (no entity ; shopper role) this means you are not logged in.

3. Attempt to log in
4. View source code again and look at line 14

<!-- v=2012.2.0.90 db=115 c=TSTDRV329799 n=2 rg=1 e=350 r=1013 ct=CUSTOMER isstore=T https=T id= cat= sc=10 sct=CHECKOUT thm=153 cart=6001 (serno=1) price=6 cur=1 lang=en_US partner=0 promocode=0 leadsource= sobcform=88 sco=F page(candbc=F fromdbc=F vol=F) -->

where e=customer ID and r=custom customer center role ID. 
This means you are logged in.