You can see that they included browser specific prefix for Firefox and Chrome/Safari, that is -moz-* and -webkit-* respectively and left out (although not every

You can see that they included browser specific prefix for Firefox and Chrome/Safari, that is -moz-* and -webkit-* respectively and left out (although not everywhere) the Opera's one (-o-). So yeah, the CSS won't work wheter the Opera implements these preview features or not. And I'm sure it implements most (if not all) of them. But to be fair, the CSS itself should work as soon as the specification is closed and browsers implement it under the regular names, without those prefixes. edit: Here is the list of attributes supported by Opera http://www.opera.com/docs/specs/presto26/css/o-vendor/ http://www.opera.com/docs/specs/presto26/css/o-vendor/ (you can see that transform, the one left out in the first example, is one of them)