When creating HTML pages, it can always happen, that you include images into a page that can not be displayed. There are several reasons for this, for example when there is a typo in the source code or the image file has been moved or deleted.
The example below shows how to do it: an image file named missing-image.jpg should be inserted. If the image can’t be loaded, the onerror event is fired and loads the file default-image.jpg in the event handler. This could, for example, be a neutral graphic, e.g. with the caption “Image not available”, etc.
<img src="missing-image.jpg" onerror="this.src='default-image.jpg';" alt="Missing Image">