Whether it’s filling in a contact form or entering profile details into a new application, handling input errors can be the difference between a good or a bad user experience.
Two examples are provided: email address validation and number validation. That is, the form will not be submitted until and unless the user provides valid data for both items.
The use of the fake button and the distinction between the fake button and real button is explained in the dropdown-nag entry.
So to start off, create yourself a little HTML file, like this.