I have tried both "cannot be blank" and a validation rule "field is blank". I have ticked the "show dialog messages immediately" option. Trouble is, if you just tab past the field, the rule doesn't fire! So I get the annoying "some rules were not applied" message on Submit, and no obvious clue as to which has failed. If I enter text, tab away, then tab back and delete the text and tab away again, the rule fires and the popup appears. It would be much more intuitive to get this to fire as you tab away from the field if it is blank.
Suggestions? I thought of coding for a lost focus event perhaps, but I really want to avoid code as others will have to follow in my footsteps!
Thanks in advance!