One major improvement that SharePoint Designer offers compared to FrontPage 2003 is that it provides a single interface to create all content associated with SharePoint and non-SharePoint sites. The New dialog box, as shown in Figure 4.3, provides an integrated user interface that allows you to create Web pages, Web sites, and SharePoint-related content.
Depending on the type of Web site being worked on in SharePoint Designer, the New dialog box shows and hides the user interfaces available to you.
The Page tab in the New dialog box allows you to create Web pages and other file types by using a list categorized by the nature of the Web content:
ASP.NET: Filters the General list to ASP.NET-specific Web content. Also allows you to create new ASP.NET web.config files, site maps, and Web user controls
CSS Layouts: Allows you to choose from a list of CSS layout templates that can be used to lay out Web pages based on style sheets ...