Depending on your needs I also recommend Selenium; highly (both the IDE and the server for running automated tests). Keep your markup clean and your semantics correct and layout neutral (e.g., "sub_nav" is far better than "left_nav" as an Id) and changing your layout may not have any effect, or minimal, on your JS anyway.
- [jQuery] How can I test my javascript? Matt Wilson
- [jQuery] Re: How can I test my javascript? Ariel Flesler
- [jQuery] Re: How can I test my javascript? Josh Nathanson
- [jQuery] Re: How can I test my javascript? Ashley