Controls..which is wrong. Those are actual User Controls.
Custom Controls are deriving from either System.Web.UI.Control or System.Web.UI.WebControls.WebControl. (Webcontrols have additional UI properites). They are customized by overriding the Control's Render method with HtmlTextWriter. User Controls are basically .ascx files.
A simple Custom Control:





















To use this custom control in your page, you need to register it with Register directive before you can use it.










User Controls are quite frequently some header and footer files. e.g. footer.ascx







You can drag the footer.ascx directly into your page, while Visual Studio will take care of the registration and implementation. e.g.









It worths to metion that, a User Control with VB.NET can be used in C# pages.
Not only header and footer are common User Controls, but any .aspx page can be converted to a User Control by changing

into

Just write this article to clear some concepts in my mind on the road to prepare 30-315 exam. Hope helps someone.