I clicked on that link and my debugger actually stated that the error is in a .js file on the geocities site. The name of the file is ygIElib9.js and you can find the path to it by viewing the source of the original goecities HTML document.
The .js file was huge so I can't even begin to think of the cause of the error message. However, in the process of reporting the error to geocities you can give them the information I have provided. Or, you can find the path to that .js file, then type that into your browser's address line, save and view the .js file and try to debug it yourself. Not that you'll be able to change it since it's an error on their site. (I'm assuming you don't have admin access to geocities web server... I could be wrong)
Good Luck..
TW
