My web site is XHTML strict, but a script I am using will not work in XHTML

strict. what should I do?
The Script is a javascript section that allows dropdown menus to appear when hovering over navigational buttons

At:
http://nicksastronomy.com/Guestbook
you can see how they are meant to work (This page is not XHTML strict)

At:
http://nicksastronomy.com
you can see what they do with the XHTML strict doctype tag.

Also, you will notice the difference between the two when right clicking, the same thing causes that.

Please note: These problems only exist when using Firefox web browser.
The guestbook script is working fine, its not the problem.

Also, the script to make the drop-down menus and nav bar are direct copies from websites (button generator etc). I'm not sure which part of the code isn't working and which part to change, thanks.

You could either re-write a portion of the script, or find one that outputs in XHML. It should not be too hard to find one that uses XHTML. Search SouceForge.org for some open-source guestbook software. Check each product's website and see if it is XHTML compatible.