The jquery UI library interferes with existing classes


Ive just had added the jquery ui library to a web page.

It appears that without even calling any its functions, it manipulates an unrelated div element which coincidentally has the css class name 'accordion'

This is really bad design imo, is this functionality by design?

If you are not using the $(selector).accordion() function it won't manipulate your DOM.
BUT because you have a class="accordion" applied on an element, and I assume that you have loaded the jquery.ui.css with the js too, the default 'accordion' styles will get applied on your elements.