This is the software publisher's description.

Adobe Dreamweaver software is the ideal tool for web designers, coders, and application developers of all levels. Enhanced coding functions make it a breeze to navigate through complex site pages at design time. Improved layout tools bring expedited workflows, from comp conception to client approval. Innovations throughout the Dreamweaver beta can help teams and individual developers alike reach the next level in performance and functionality. Download the pre-release of the next version of Dreamweaver now and send us your feedback. The Dreamweaver beta will expire soon after the next version of Dreamweaver is available for purchase.

New features include a live preview mode, so you can see how your web page will appear in different browsers. There is a related files option, so you can see files that relate to a particular web page. There are many other code-related improvements as well as a brand new user interface that looks very different from the current (CS3) interface.

Important: This is a public beta, not a final release. Neither the quality nor the features are complete yet. We want to show you our direction and get your feedback so that we can incorporate it into future releases.

Note the download here takes you to the Adobe Labs page where you can obtain Dreamweaver CS4. You need an Adobe CS2 or CS3 serial code to obtain your CS4 code.