Hi Brian - There is a program you can import from the Marketo Program Library that has a landing page template that meets the Facebook specs so no scrollbars appear.
Import the program called "Facebook Tab Template" from the Marketo Program Library.
Here's more how-tos on importing from the Marketo Program Library:
Hi Brian, the problem could be the way you've designed your landing page. Your landing page might not be responsive. Try to do one thing, decrease/increase the zoom of the browser window in which your landing page is running, to make sure that your landing page's width decreases/increases with the change in zoom and the elements used in your landing page(like image, form, etc) don't fall out of the flow of your landing page design. This test is done to ensure that no scroll appears in the landing page in any viewport of the browser window. If you get any scroll, try to consider testing your LP's design.