I am creating a family website. My goal is to give eligible family members individual accounts with their own user name and password, and create seperate albums for each user that they can upload and edit.

I understand the basic concept of how to do this, and can do it. However, I am uncertain about one thing.

I test the accounts myself, by signing in as the individual user to make sure it all works. However, does this set anything (especially cookies)that would prevent the intended user from being able to sign in? If they log in and try to edit, will it also accept their computer and url as valid?

Whenever you login a cookie is set in your browser. When you logout it is cleared. So, if all your family memebers are using the same computer you will have to instill some disipline on having them logout.

If everyone is on different computers there is no problem. The user/passwords you create are accepted anywhere they are presented.