luiscmas on "[Plugin: Contact Form 7] onClick="return window.confirm"

http://wordpress.org/support/topic/plugin-contact-form-7-conditional-redirect?replies=15
http://contactform7.com/tracking-form-submissions-with-google-analytics/

Maybe this would help you

You will find the Additional Settings field at the bottom of the contact form management page; now simply insert the following line into it:

on_sent_ok: "window.confirm('ok');"
Note that you need to quote the codes properly and the code must be in one line.