Hi Andrew,

The out of bounds notification shows where elements on your page will be outside the standard width of the screen on a mobile device or desktop. It might only be a pixel or two, but if elements are outside the width of the screen, the browser will show a horizontal scroll bar.

You might not notice this if you are previewing on a larger monitor.

Since a horizontal scroll can detract from the user experience when visiting you landing page, we recommend keeping all the visible elements “in-bounds”.

Hope that helps.