Sorry to post two in quick succession!
I'd like to integrate this into other forms. I have a custom contact page form that I've written and at the moment it calls itself for validation and redisplays the form with inline error messages if fields have not been completed.
I'd like to make it consistent with the comments and use this plugin. I can handle putting the right css containers in, I just need to know what the validation code needs to do to trigger the messages.