Sub pages jumping into password page

I’m building a site and put a password into index.html : and it works fine and redirect to intro page which is another html page, the page I have is aboutus.html, contact.html, porfolio.html plus the index.html… my problem is when I checked my complete url directly to contactus page .eg" mywebsite.com/contactus.html" it passthrough to the password page which i put in index.html, what codes do i have to put for for my sub pages html? so that my visitor will not jump to any subpages, and if they intend to enter they will redirect to my password page, and with that they can access the whole site page when they enter the password. Any code help will be appreciated!
Cheers!