I would check the security settings of your browser to make sure running scripts is enabled. It's also possible that there's either an error in the script or a bug in your browser. You'd have to post your operating system, browser and version, plus the url of the image you're referring to, for anyone to really be able to offer detailed help.
Give a man a fish, he'll eat for one day. Teach a man to fish, he'll drink all your beer.
Cheers, Jeff (SCJP 1.4 all those years ago...)