Dont use include() to add the registration page:
include('registration.php'); // Terms page
That is not a very good way to add a page to another as the php code on the registration page above the doctype will now be in the body of the trial page, and it will also include multiple head and body sections.
Instead, Use framework Builder Dynamic Plugins
Open the bindings panel. Click the plus button and create a new URL variable binding, name it key
Then go to WebAssist -> Framework Builder -> Plug-in -> Insert Dynamic Plug-in
for the trigger variable, select the key URL variable. For the Plugin source, select the registration page, and the variable value use reg