By editing the settings of a page, you can specify that access should be restricted to contacts who meet certain conditions (more here). Automation can be used to place contacts into groups after form submissions, and you can add a password field to signup forms to allow contacts to set a password.
You can also code your own login forms and restrict access to certain pages or content if you wish. The following article shows a typical implementation of a login form on a Oncord powered website.
Determining Whether a User is Logged in
The <ss:logic:if> control allows you to check whether a user is currently logged into the website. This will allow us to display different content to users, depending on whether they are logged into the website.
The Login Form
The following code is a common implementation of a login form, wrapped in the above <ss:logic:if> tag to determine whether a user is logged in: