See the movie at http://www.screencast.com/users/loeribas/folders/Jing/media/6b3a893d-d97b-4801-8e1d-0f5e567da7db The left browser is Firefox, the right one WebKit.
The website (<http://www.volkskrant.nl/vk-online/resources/stylesheets/paper.css>) uses "-moz-opacity:" and "filter: alpha()", which are Gecko and IE extensions, respectively. WebKit supports the CSS3 "opacity" property (<http://www.w3.org/TR/css3-color/#transparency>).