Adobe has made available an extension which provides initial support for HTML5 and CSS3 in Adobe Dreamweaver CS5, and helps you easily create HTML5 pages and CSS3 styles. It also includes updates and WebKit improvements for Design View and Live View rendering.

While HTML5 and CSS3 will not be finalized for some time, the extension provides support for a set of currently-implemented features in Adobe Dreamweaver CS5.

This extension enhances Dreamweaver CS5 in the following ways:

• Introduces the Multiscreen Preview panel , allowing for Live View display on 3 different screen sizes, with Media Query support. (Window > Multiscreen Preview)
• Adds code hinting for the HTML5 Tag Library with new tags, attributes, and properties.
• Updates code hinting for new attributes and values in existing HTML tags.
• Adds code hinting for the following CSS3 specifications: 2D/3D Transformations; Animations; Background and Border; Basic User Interface; Line Layout; Marquee; Media Queries; MultiColumn; Ruby; Text; and Transitions.
• Updates Live View to support < video > and < audio >. (Requires Quicktime installation.)
• Improved rendering for CSS3 in Live View.
• Adds HTML5 starter layouts to the New Document Dialog box.
• Offers better rendering for new tags in Design View.

You can download the HTML5 Pack here.