These tooltips don't work properly in FF11. If you have them in a div that overlaps another, or have the tooltips attached to images in said div, the tooltips will appear behind the images next to it. Z-index doesn't work to change this.
I think it could be because I have a ulist where the li elements are displayed horizontally using display: inline and no-style, and maybe this messes up the display/parent-child relationship.