One of the lowest low hanging fruits I see browsing the web today is layout shift when an obtrusive scrollbar toggles on/off.

It happens when navigating between pages of varying length. It happens with poorly implemented menus/modals/dialogs that toggle `overflow: hidden`. It can happen when a particularly heavy/long page progressively renders.

`html { overflow-y: scroll; }` can fix it for some of these cases.

But primarily: test for obtrusive scrollbars, please!