Reference from Inside Microsoft Windows SharePoint Service 3.0

difference between site pages and application pages. Site pages support page customization. Examples of site pages include the home page (default.aspx) for a site as well as the pages associated with lists and document libraries, such as AllItems.aspx, NewForm.aspx, and EditForm.aspx. The fact that site pages support customization provides flexibility but can also impact performance and scalability. Site pages do not support in-line code under the default security policy enforced by WSS.

Application pages do not support customization, which gives them two distinct advantages over site pages. First, each application page is always compiled into a single DLL so that it performs and scales better than a site page. Second, application pages are allowed to have in-line code. Now that you have a basic understand of what constitutes an application page, it will be worthwhile to see what is involved in creating your own application pages for a custom solution.

each of the virtual directories within a Web application maps to a physical directory on the file system of the front-end Web server under the following path:

c:\program files\common files\microsoft shared\web server extensions

Each of these virtual directories plays a special role in the overall WSS architecture. For example, the _vit_bin directory provides WSS with a way to expose DLLs and .asmx Web service files at a path within the URL space of a Web application. The _controltemplates directory provides a dedicated repository for deploying ASP.NET user controls that can be used within pages. The _wpresources virtual directory provides a repository for resource files that are deployed along with Web Parts.

The one virtual directory of a Web application that we want to discuss in greater depth in this chapter is the _layouts directory because it provides the foundation for a special type of page known as an application page. Application pages are served up from the _layouts directory and provide a special type of functionality that is discussed in the next section.