An article I worked on has recently been published to MSDN. The article, Approaches to Creating Master Pages and Page Layouts in SharePoint Server 2007, demonstrates the two different options available to developers when creating custom master pages and page layouts within a MOSS 2007 Publishing site.
Here's a summary on what the article is all about:
Every Microsoft Office SharePoint Server 2007 publishing site-also known as a Web content management (WCM) site-consists of one of more master pages (.master files) and page layouts (.aspx files). Each type of file serves a specific purpose. The master pages, also used in traditional Windows SharePoint Services 3.0 collaboration sites, contain the overall appearance ("look and feel") and branding of a site. They contain elements such as cascading style sheet references, common navigation components, search controls, and the typical header and footer seen on all sites. Page layouts are used to define the specific rendering of content pages, or where content is found on the page. Just as in Microsoft ASP.NET 2.0 sites, page layouts are merged with master pages at run time to generate the complete page.
These two types of files are very similar to those found in ASP.NET 2.0 sites, but the process of creating and deploying them is very different in Office SharePoint Server 2007. In fact, in Office SharePoint Server there are two ways to create and deploy these files. As a developer or a designer, you should be aware of both approaches and the advantages and disadvantages of each before embarking on the next Office SharePoint Server 2007 publishing site project.
The primary reason for the difference in the master page and page layout creation process between ASP.NET 2.0 sites and Office SharePoint Server is due to the architecture of the SharePoint platform. In Office SharePoint Server, the file system of a site lives in a database, also known as the virtualized file system, whereas in an ASP.NET 2.0 site the files are on the file system.
This article explains the virtualized file system and then discusses the different approaches that you can use to create custom master pages and page layouts for use in an Office SharePoint Server 2007 publishing site.