Very cool!
Maybe an improvement: there isn't much constrast between the text and the background of the popup hint (at least on Firefox Nightly on Linux: http://i.imgur.com/hqrF5.png).
Maybe an improvement: there isn't much constrast between the text and the background of the popup hint (at least on Firefox Nightly on Linux: http://i.imgur.com/hqrF5.png).