HttpHandler not firing from body of .aspx page

I have a http handler that is called from a .aspx page in the form 1x1 pixel image. The h开发者_开发知识库andler has an extension of .jpg set up in the web.config. On all browsers apart from IE the http handler is called successfully from the body of the page when it loads.

However in IE the httphandler is not called.

If I call the http handler by entering the url in to the address bar in IE it works perfectly.

Any idea why it might not work in the body of the page?

IE may have it cached the image. If the filename of the .jpg isn't changing, I'd try to add a random query string to the end of it.

http://<path>/0104924934404624104049.jpg?random=<unix timestamp>