I have a Javascript error in my page, what to examine/do first

When having a JS error,
first thing to look should be if jQuery AND/OR jQuery UI is loaded only once.

you can find this by doing "View HTML source" in your browse and searching for 'jquery'

1. ALTERNATIVE 1: The loading of jQuery is handled by Joomla in J3.x (so this problem should be rare in J3.x), but in J1.5/J2.5 there is no easy way to load jQuery/jQuery UI only ONCE other using a extension for this purpose
e.g. jQueryEasy extension
(which will add a 0.1-0.3 seconds to all your pages ... depends on your server, but it will also reduce loading page for your first-time visitors by 0.1-0.2 seconds, if you select to do the loading jQuery from a common server like Google servers)

2. ALTERNATIVE 2: we (FLEXIcontent) have an option to disable automatic loading of jQuery in frontend (it is in component parameters), so disable the loading of in FLEXIcontent and in all other extensions that load it:
e.g. (extensions)
- disable in FLEXIcontent
- disable in Virtuemart
- disable in Widget
and load it your joomla template (e.g. in index.php) by adding script HTML tags (for JS and link HTML tags for the CSS)

-- if the above is not the case the go ahead and post in our forums