"Validation errors" on Firefox and Safari

I’m getting “Validation errors occurred. Please confirm the fields and submit it again.” when I try to use my contact form on Safari and Firefox. It seems to work fine on Chrome. I don’t see any HTML or CSS errors using Firebug. Can anyone more knowledgable help me out?

Site: http://www.nonsensesociety.com/contact/

Thanks!

https://wordpress.org/plugins/contact-form-7/