I have a form with a checkbox that prompts the user to agree but somehow the form gets submitted anyway right after the user clicks okay in the alert box. Is there any way I can stop this from happening?
The form is at...

<http://www.dreamhomevacationrentals.com/hotels/spanish-modern-retreat/>

Click "Availability" from the left side menu and then click the blue "Book Now" button to see the form in action.

Any help is greatly appreciated.