HTML if image is not found

Question

In an HTML page, I have an image:

<img src="smiley.gif" alt="Smiley face" width="32" height="32" />

If the image cannot be located on the server, an unsightly blank square is displayed.

If a picture cannot be found, I want it to display nothing or an other default image that I know is present on the server.

How is this accomplished?