In my Blog category page, I set 3 columns of posts. It’s ok in PC and Tablet mode, but not good in mobile mode. The alignment of column is not on center, but moving into the right a litte (looks like the image).
I used 420px as i had it to hand in some other code i was working on 🙂 as it covers all the current Plus Size Mobile devices. You can bumpy it up to 767px, this will work without effecting Tablets.