Several ASCX controls exist within an ASPX file.

One of the ASCX controls has a couple of asp textboxes and a link button.  

The form submits when the link button is clicked.

But, the form does not submit when the cursor is on a textbox and the 
<enter> key is pressed.  Does anyone know why the form does not submit 
when the <enter> key is pressed?

thanks in advance