<!DOCTYPE html>
<html>
<body>
<img src="image.gif" onerror="myFunction()">
<p>A function is triggered if an error occurs when loading the image. The function shows an alert box with a text.
In this example we refer to an image that does not exist, therefore the onerror event occurs.</p>
<script>
function myFunction() {
alert('The image could not be loaded.');
}
</script>
</body>
</html>