To deliver the best user experience, placeholder and fallback elements should be used when appropriate. Placeholders are displayed in place of an element until that element is ready to be rendered, while fallbacks are displayed instead of an element when the element is not supported in a browser.
An element with the placeholder attribute acts as a placeholder for its parent. Placeholders are displayed immediately for an element, before the element has been downloaded or initialized. When the actual element is ready, the placeholder is hidden, and the element content is displayed.
Thus, placeholders can be used to stand in place of a slower-to-load element. You might use this, for instance, to display a fast-loading, low-resolution image in place of a video or high-resolution image. The latter is the same trick that sites such as Medium (medium.com) and Facebook use to deliver a quick page-loading experience. They show...