I'd assume that there is some automated testing happening to make sure things are working, and I bet there's some manual testing too -- but I also bet that the

I'd assume that there is some automated testing happening to make sure things are working, and I bet there's some manual testing too -- but I also bet that the automated testing doesn't do visual comparisons (I've never seen a company do it), and I bet that standard issue computers were macs. You visit the page on your dev computer, your phone, check Jenkins -- everything looks good, publish. Oh, but then production notices how not-good it is. It's really easy to miss these kinds of things, and the solution always seems obvious in hind-sight, otherwise clients would never find bugs.