Detecting Flickr image redirect to photo_unavailable image

Provide browser based javascript code that will detect when a Flickr photo is not available and then display another image in its place. [login to view URL] code shall work with a standard html img block. For example: <img src="[login to view URL]"> [login to view URL] javascript code shall work in Chrome, IE, FireFox and Safari. [login to view URL] when an arbitrary flickr image url is redirected to the photo_unavailable image. For example, the image url used for item 1 above, will be redirected to: [login to view URL] [login to view URL] code shall make a callback to a function that will provide a substitute URL for the unavailable url and then attempt to display the substitute image. For example, the following url will render correctly: [login to view URL] [login to view URL] user shall not see the photo unavailable image, since the substitute image shall be rendered in its place