When to build a custom integration for the Experience Manager Web site extension
Build a custom integration if your Web site does not serve content directly from disk.
The installation instructions for the Experience Manager Web site extension will work if your Web pages are served as files directly off of the Web server. But many actual Web site implementations, especially MVC-based implementations, use custom algorithms to turn an incoming HTTP request into dynamically served content.
The pieces of content assembled into the HTTP response may reside in a database or elsewhere outside the Web site's virtual folders. In fact, the content may not exist at all and be dynamically generated at request time.
In all such scenarios, the Experience Manager Web site extension needs to be integrated with your Web site.