I have generated a Web-to-Case form and placed it in a Visualforce page the is on a Sites page. The retURL is directed towards another Visualforce page and I've set the object permissions and the public access settings. When the "Submit Button" is clicked, it just takes the user to a salesforce login screen and not the desired Visualforce page. I'm not quite sure what the issue is. Should a I be using a controller?
The return URL is of type
retURL ="https://c.na30.visual.force.com/apex/thanks"