Customized Submit Button Not Working

I changed the image of the submit button, following the instructions at http://www.fastsecurecontactform.com/submit-button-image or so I thought.

Apparently I missed something, as the button on my form at the bottom of http://instantpracticebuilder.com/tu4b6ypo/module-10-completing-your-self-analysis-by-using-the-tows-matrix/session-51-turning-your-competitive-strengths-into-resources-and-capabilities/ is not working.

What did I miss?

http://wordpress.org/plugins/si-contact-form/