How to redirect back to a post after registration

Hi,

When my clients user click login in the bottom of any post, and add their info, they are redirected back to the post they just read. This is working just fine.

However, if they click on the registration link "Tilmelding Gratis" ( please see http://net2change.dk/indre-og-ydre-motivation/ ), then they are redirected back to the login page. How can I change that so they are redirected back to the post they just read.

I have used the same class for the signup link, however, it doesn't seems to be working as the login feature.

Sincerely,
Mika