Question

You should use html elements instead of server controls when

Answer 1

The server controls are the controls used to get data entries from users and to display data for users. When a form is displayed in a browser then these controls are rendered into HTML elements.
You should use HTML elements instead of server controls when the data in the controls isn't going to change. However in situations in which you don't know how to code the HTML elements, then you should use server controls even though the data in the controls isn't going to change.