Thanks for the tip Kathryn!
It’s currently under construction but it’s visible on the sela theme (https://wordpress.com/themes/sela/). It’s just the grey borders on the left and right edges surrounding the content.
I attempted to change the values of padding in the editor for .page and .site and that didn’t work.
HELP!!!