When I change the height of a page so that the vertical scrollbar appears, a div element on the page stretches out and a blank block appears at the bottom of the page. The current site is here:
What should I do to stop this resizing of the div? Should I just disable the vertical scrollbar altogether?
For posterity, I’ve added a few screen shots.
Without scrollbar:

With scrollbar:

This is your culprit within the /assets/application-67b0f50f40b31242c0515ffd40544866.css file the @media-queries css kicks in at a certain screen height.
find this line and take out the margin-top: 271px; and you should see the extra spacing disappear. You won’t need to disable the scrollbar. I hope this helps.