Can I display an "image not found" image in HTML?

Until just a few days ago, I would have said "I think you're out of luck" or would have suggested that a more efficient dynamic page generating CGI script would have been the way to go (after all, transforming a directory of images into rudimentary HTML to display those images isn't too difficult to program, in my experience) but now I do have an answer for you!

What's interesting is that the answer is from the nether region of markup where it's not truly JavaScript, but it's also not really HTML, it's an error handler script similar to the "onClick" and "onLoad" event handlers that you might already be familiar with (I talk about them at length in my book Creating Cool Web Sites with HTML, XHTML and CSS, but I never bumped into this particular event handler when I was researching the material so this is new stuff even for people who have that book).

The event handler is onError and apparently you can tie various JavaScript actions to a specific HTML tag, including the "img" tag, by using it in a savvy manner.

In this case, we'll want to tweak an IMG tag thusly:

That's how it apparently works, so if you have 'error.gif' set up as an error image, perhaps saying something like "Image no longer available", you should be able to achieve the exact results you seek.

There are other places where it'd be interesting to experiment with onError too, for those of you wanting to hack around a bit. For example, put it in the BODY tag and you can pop up a window warning people that something went wrong loading the page and that they should check their error window and perhaps email the results to you so you can fix the problem. If you do experiment with this nifty attribute, please do post a comment so we can all learn what you can and can't do with it.