This is the complete URL to your "Thank You" page to display to visitors who complete your form. If you are running a viral campaign, make sure you put the Send2Friend code on this page for the linked campaign (see step 3 below).
Putting an email address in here will ensure that you get a copy of each form submission via email as well as the data being stored in your collection for download. (NB: Using this feature is the equivalent to having an additional "FormMail" script).
By optionally selecting a Send2Friend campaign here, you can run a viral marketing campaign that incorporates data capture as well as Web site referrals. Note that if you are using the Send2Friend codeon the collection redirect URL page (see step 3 above) then it is crucial that you put a static URL in your campaign (see Edit Campaign).