How to: Add HTML Server Controls to an ASP.NET Web Page Using the Designer
Adding HTML server controls is like adding any HTML element, except that you convert the element to a server control so that you can work with it in server code.
For information about controls for Web Forms pages, see.
To add an HTML server control to an ASP.NET Web page using the designer
From the HTML tab of the Toolbox, drag an HTML element onto the page.
Convert the element to a control by right-clicking it and choosing Run As Server Control.
Visual Web Developer adds the attribute runat="server" to the element, which causes ASP.NET to treat the element as a control. A glyph () appears on the control in Design view to indicate that it is a server control.
For information about adding controls directly in the .aspx file, see How to: Add HTML Server Controls to a Web Forms Page using ASP.NET Syntax.