First things that leap to mind are that you have no valid URL DOCTYPE for the page, and/or - because the script you say you are using is a bit dated, it just isn't up to the task. The latest version is 2.04. The one you linked to in your post is version 1.0.
Anyways, I could be wrong about part or all of this. The only way to really tell would be to have a link to the page so we could be able to snoop around it and see what's what:
Please post a link to the page on your site that contains the problematic code so we can check it out.
Now I know you said the page isn't up anywhere yet. But you also said that it could be if required for us to help you. It is.