Why is there a white gap on the right side of my site on mobile?
This is normally caused by some element on your page that's too wide. When you set element widths in px values, they don't scale. If you have an element that's 500px wide but the viewport is only 300px wide, you'll end up with a white gap on the right side of your site.
To identify the cuplrit, you can use Mike's tutorial:
In some cases, it can be caused by an element that's animated in from the side using the Animate on Scroll feature. You can tell if this is the case, because the gap will go away once you've scrolled to a certain point on your page. If that seems to be the cause, you can add overflow: hidden to the container of the animated element to fix the issue.