Opacity or filter applies to all content in the same element, so the only way you can get text or an image with no opacity over a background that has opacity is to layer it, using a div or another element that isn't nested and it needs position: absolute or position: relative to reposition it over the element with opacity.
I've never tried that with an accordion menu.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.