If someone forgets to fill in a field, which one looks the best?
Required field: First name
YOU MUST FILL IN ALL REQUIRED FIELDS!
This form requires that you fill in all fields before submitting. Please check the form and review all required fields to make sure they are completed. Required fields are highlighted in RED with an asterisk next to the field.
Cheerio, jolly good day outside isn't it? By the by I noticed that you may have forgotten to fill in one teensy weensy field. Would you mind lending a hand by filling that field out if it's not too much of a bother? Thanks in advance.
As comical as these may seem, I've seen some code that was pretty close to some of those examples.
When in doubt: Keep it simple, and avoid SHOUTING !! with caps lock or exclamation points.