Simon Willison’s Weblog

Let’s go ::outside

Tom Gilder has started a series of posts looking ahead to CSS3. In his first installment, he describes the awesomely powerful ::outside pseudo-element. Using this, CSS3 authors can apply multiple backgrounds and borders to single elements (at the moment doing so requires fussing around with nested divs). If you don’t instantly see the importance of this, take a look at some of the attempts to render rounded box corners using CSS. All of them require the addition of extra presentational elements, none of which would be needed if we could use the ::outside selector instead.