Thanks for contacting us.
Based on your scenario, anonymous comments have been denied in the forums and since your user isn't logged in, he or she isn't able to post. To disable this feature, you could go to Modules > Forums
and then click
settings next to the forum. Click allow under anonymous comments and you should be all set.
The login control from the Sitefinity toolbox is the same login control from Visual Studio, so it has all the same properties. Simply click edit on the login control, then the edit button next to the login box to see all of its properties. The one you want is DestinationPageURL and that's located under Behavior section. For more info on that control, please read this MSDN article
I hope that I have provided a solution to your technical issue. Let me know if you need further assistance.
All the best,
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.