There is a minor bug in the Divi Theme which causes the horizontal scroll bar to be shown and allows the user to scroll a little bit past the edge of the main blog. Here's how to fix it.

First, an example of what I'm talking about.

divi theme scroll bar bug

Notice that the horizontal scroll bar is showing, and that having scrolled as far as I can go, I'm now slightly off the side of the page and can see the edge of the header bar.

It took me a while to track down the culprit. All the visible components of the screen were correctly staying within the bounds of the normal screen size. The offending component, then, had to be something invisible! Turns out it is the drop-down submenu which causes the problem, as can be seen here:

divi theme scroll bar bug - submenu

So how do we fix the issue? It's as simple as adding the following CSS to the theme:

#page-container { overflow:hidden; }

This forces the part of the menu which spills over the page to be hidden from view. The result is that the horizontal scroll bar is no longer shown and you can't scroll past the edge of the screen.

Here's the final result. Notice the lack of horizontal scroll bar this time:

divi theme scroll bar bug - fixed

The fix doesn't seem to cause an issue actually accessing the menus. But be sure to check on your own site just to be sure.