Adobe announced at the Google I/O event last week that it had a free downloadable add-on module for Dreamweaver CS5 that extends the program to offer robust HTML5 and CSS3 support. Dreamweaver CS5 has been shipping only since 30 April 2010 as part of the Creative Suite 5 set of applications.

While Adobe has been fighting to promote Flash as a cross-platform tool for mobile devices, mentions of HTML5 and CSS3 have been scant. Adobe makes tools that produce audio, video, Web, Flash, and other content, and I had been hoping that along with its full-frontal promotion of Flash, it would also be working hard to create good tools for creating pages that rendered well in the next generation of browsers. (For more on the Apple/Adobe tiff, see "Jobs Explains Apple's Position on Adobe Flash," 29 April 2010.)

HTML5 and CSS3 go hand in hand to deliver a more nuanced browser experience. HTML is used for defining the content and structure of a page, while CSS controls the display and appearance.

HTML5 has many new features, including semantic tags to identify parts of a page by content, tags for audio and video to embed media, a "canvas" tag for rendering vector graphics and images, and other multimedia support. Although HTML5 defines these tags, Web browsers will have to implement the tags in the same way for playback and display of the associated media to provide a consistent user experience.

CSS3 enables designers to make Web pages with the kind of subtle interface choices found in desktop and mobile applications. For instance, support for rounded corners on boxes, custom borders, and graduated shading can make buttons and other elements fit into an overall design better without the use of static images. CSS3 also supports multiple-column layouts.

CSS3 is more or less baked, while HTML5 continues to lurch towards completion. Opera (10.1 Mac, 10.5 Windows), Safari 4, and Google's Chrome have the best support for both in-progress standards at the moment, while Firefox 3.6 lags behind. Internet Explorer 8 handles almost nothing HTML5 and CSS3 have to offer, but Microsoft is promising good support for both standards in the forthcoming Internet Explorer 9. FindMeByIP.com has a marvelous feature-by-feature compatibility list for each browser and platform.