Design view is a convenient way to visually edit and test your web pages before you publish them to the web.
Microsoft Expression Web can preview HTML, ASP.NET, and PHP pages.
There are three preview options to test your pages:
Previewing pages You can test a page in any browser installed on your computer.
Snapshot Panel You can see your page in the Snapshot panel as you edit it.
Displaying pages in SuperPreview You can compare how elements in your pages render in different browsers.