ASP.NET
Default Buttons

This non-visual control allows you to assign a button to the
“enter-pressed” clientside event of input controls. This makes it
so that when the user presses Enter while in a textbox, the form
will postback, and the serverside click event of your button is
fired. The is done on a per-input-control basis. In a visual
designer like Visual Studio or Web Matrix, this control will add a
“DefaultButton” property to the properties window of the other
input controls on the form. There are sample files showing how to
set it up with a text editor.

Particularly useful within user controls where you may end up
with multiple user controls per page, each preferring a different
default action.