This looks like very bad idea to make a page looking different for users based on their cookies. When user comes to this page from different laptop, he will get

This looks like very bad idea to make a page looking different for users based on their cookies. When user comes to this page from different laptop, he will get confused since the highlighted button won't be the "Sign in" anymore as he got used to. I guess Sign In and Sign Up should be distinctively different all the time.