[Help] Signout problem .. Still log in in the main page only

Hi every body
 
I have a strange problem in my website. When I log out from the site and try to type the URL of the main page (first page after login) it shows it as logged in, While other pages are ok, Also when I refresh this main page it returned to the login page
 
I tried to ways of log in and log out (FormAuthentication & Seasons)
 
Any help please
^_^
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