Validate ddl selection on page load event?

User's previos ddl selection is saved and then attempting to select it for them on page load. What to do if selection no longer exists - msgbox in page load seems like something that should not be done. How can I notify user that their selection no longer exists so the ddl selection is being reset to default?What about using a label to display the error message? Set the Label Visible property to False in the designer, then if the selection no longer exists in Page_Load, set the Label Visible property to True. If you are wanting to present an error message in a popup dialog similar to MsgBox, that requires client-side code.