An ASP.NET theme is a collection of styles, property settings, and graphics that define the appearance of pages and controls on your website. A theme can include skin files, which define property settings for ASP.NET web server controls; cascading style sheet (.css) filesthat define colors, graphics, the size and placement of controls.

The Microsoft AJAX Library is actually written in JavaScript. It is a set of files that are sent to the browser to provide a base of capabilities on which we can build. ScriptManager control automatically injects these scripts into the page markup when needed.

A user control is a file we create that contains a set of other ASP.NET controls and code grouped together to provide common functionality. The user control can then be used on different pages within a website.

We store and retrieve user profiles in a database by using SqlProfileProvider class. This class abstracts the storage and retrieval of the profile information from the actual profile itself.

Useful login controls to authenticate users:
1. CreateUserWizard
2. Login
3. Loginview
4. Loginstatus
5. Loginname
6. PasswordRecovery
7. ChangePassword