Javascript Form

Hi!

I’m having some trouble with a newsletter sign-up form on a web site I’m working on.

It seems that the form shows up on my computer which has the latest version of Firefox but on another one of my computers which has Internet Explorer version 6 and an older version of Firefox it doesn't show the form at all in the popup box. The form appears on the page, but at the very bottom of it, not in the popup box where it should be…

I got the code for this form from AWeber Autoresponder & Newsletters: Unlimited Follow Up Autoresponders Increase Email Deliverability, and I'm wondering if this happening because of the older browsers, or the coding?

As you can tell I'm not really familiar with Javascript... Thanks for helping me.