Responsive Jumps
The shift on responsive web pages where the layout changes to accommodate the narrower viewpoint.
You can see these on your browser by grabbing the side of your browser window and making your browser get narrower. At a certain pixel width, the style sheet thinks the machine is a tablet (and then, at a narrower width, a phone), and calls upon different styling, often incorporating an adjusted-for-aspect-ratio graphic, text-size changes, replacement text for graphics, additional text-based navigation leading to content that may have shifted and stacked out of sight, and outright omissions of content.