Master Pages are an ASP.NET 2.0 feature that lets child pages inherit and re-use a common design. This only makes development and maintenance of the site much easier. New pages don’t have to re-do the work of the master. When you want to apply a new design, just change the master. Typically they will contain the branding, navigation, header and footer for the site. We used this to implement the overall “visual blueprint” of SharePoint including access to the end user features.

Master pages and page layouts dictate the overall look and feel of your SharePoint site. Master pages contain controls that are shared across multiple page layouts, such as navigation, search, or language-preference for multilingual sites. Page layouts contain field controls and Web Parts. The following figure shows how page layouts and master pages work together to create the layout for a Web page.

Turn on the master pages toolbar to quickly identify and jump between content regions (placeholders). You can find it under View, Toolbars

This code contains all the necessary content placeholders in order for the page to run. You can wrap your custom code around the placeholders and add your custom CSS file(s) in order to brand the master page.

As a quick refresher, styles applied to elements in a page will be styled according to the last property that was applied to it. An inline style will override a style listed in the HEAD tag or in a linked CSS file. Additionally, you can selectively override style properties by selectively listing what should be overridden.

…Default.Master pages are stored at each level. If they are not modified they will be pulled from the disk. If they have been customised on the disk then your changes would apply to all pages that use the “Default.Master”. If you make changes using SPD (SharePoint Designer) then the master page is moved to the database and is pulled from there.

• Introduction to Extending WCM
• Understanding the Structure of Master Pages
• Understanding the Default Master Pages
• Building a Custom Master Page
• Adding Cascading Style Sheets
• Customizing the Navigation
• Creating Custom Field Controls
• Customizing the Edit Mode Experience

Customizing Master Pages using SharePoint Designer 2007, where he warns about frontpage changing the referances automatically, and I thought I should write some best practices as I find them (will be updated in the future).

You can do a limited amount of customization through the browser, you can also customize the look and feel by applying a different theme to your site. What you couldn’t do using either methods, was change the layout completely – basically make a SharePoint 2007 site look absolutely not like a SharePoint 2007 site.

You can create a master page from scratch. However, we generally do not recommend this approach, because a truly empty master page does not include all the content placeholders that are required for the Office SharePoint Server 2007 page model to work. The sample code in the following procedure includes all of the necessary content placeholders.