Answered FormIt :how to display successmessage in modal window

In the case of demos like these, viewing the source of each page is necessary.

View the first page, when the form is first loaded. No error messages, no success messages, just the form. So your resource needs to be like that, just the form... and, of course, the FormIt snippet call, which doesn't do anything on the initial page load in this case since there's no POST (a FormIt pre-hook will do things on this page, before the form is submitted, that's why it's called a pre-hook).

When the form is submitted, then when the page is re-loaded FormIt does stuff with the POST, according to the properties it's given. Such as inserting error messages or the success message.