I'm wondering if it makes sense to have "login/register" buttons displayed on the website header. The client would be redirected anyway to the register/login page whenever it tries to access a protected resource (e.g. my account ). Still almost all the websites provide such buttons.
What if the user goes to you main page looking for a login option? They would have to try and access restricted functionality to trigger display of the login screen. This isn't friendly or obvious at all.
You could force all pages on the site to redirect to a login screen, but then where do you put the content aimed at people who have not created an account yet? If it is something simple like signing up for an email account then you can use this approach (and many of them do), but a big e-commerce site like Amazon needs people without accounts to be able to browse the same products as logged in users, albeit with slightly different options displayed.