Image Size and Responsive Images

Before an image arrives, the browser does not know how big it is. The previous lesson showed that the browser keeps building the page while the image downloads. If the <img> element says nothing about its size, the browser gives it no space at first, so the paragraph below the image appears directly under the heading.

When the image file arrives, the browser learns its size, makes room for it, and pushes everything below it down the page. A reader who has started reading the paragraph sees it jump away, and a reader who is about to tap a link may tap something else