What is an image placeholder?
An image placeholder is a dummy image designed to draw attention to the need for an actual image. Wikipedia image placeholders were meant to be used on articles, especially those of living people, for the purpose of trying to obtain a freely-licensed image for them.
How to add placeholder for image in HTML?
Whenever you load large image on the page and it's taken too much time, that time you can show loading image or you can say Placeholder image ( Html Image Placeholder ) within the same image tag. You can do this simply by using CSS. Use background property of css and set url of an loading image.