Firefox "onerror" would not fire even when image is not valid

I have a onerror handler on the image tag to handle switching when the remote image is not found.

the problem is that for certain broken remote images, it does not work.

http://a3.twimg.com/profile_images/522455109/calvin-and-hobbessm_normal.jpg

<img onerror="this.src='/images/pic_not_found.png'" src="http://a3.twimg.com/profile_images/522455109/calvin-and-hobbessm_normal.jpg">

Image below: 1) when remote image found, 2) remote image not found (onerror not triggered) , 3) remote image not fou开发者_如何学Cnd (onerror triggered)

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It is not a broken link.

The twimg.com actually returns an image with the name of the url you requested.

just click your link to the image. It is not text what you are seeing, it is an image.

Update

Here is some code that works in all browsers.
It does some basic feature detection.

function handle( elem, img, state )
{
  if ((typeof(elem.onerror) === 'function' && state === 'fail') 
      || (elem.width === 0)
    )
     {
       elem.src = img;
     }
}

http://jsfiddle.net/VVcQj/1

It uses both onload and onerror, but requires a function defined in javascript to handle the situation.