How can i make a requirement user name and password all time the user access my website?

Hi all experts,
I'm the first one of ASP.NET. At the beginning my website has 6 web form( default,w1,w2,w3,w4,w5.aspx)
in web browser, i type like this http://localhost/
it displays the default web form with the user name and password to log in. but if i type http://localhost/w4.aspx, it doesn't let me to input the user name and password.
My purpose is "All times the user access to my web site,the user need to input user name and password. Even they input
http://localhost/w4.aspx, it still display the log in web form". So how can i do that?

Thanks

TONY

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