Change the Master Page of a SharePoint 2010 Site
SharePoint 2010 includes two master pages: v4 and nightandday. By default, the master page of a publishing site is v4.master. To apply a different master page, follow these steps:
Select Site Actions→Site Settings.
The Site Settings page is displayed.
Locate the Look and Feel section.
Click the Master Page link.
The Site Master Page Settings page appears. This page has three sections — Site Master, System Master, and Alternate CSS.
Choose to have the site inherit from the parent site master by selecting the Inherit Site Master Page from Parent of This Site radio button, or apply a specific master page by selecting the Specify a Master Page to Be Used by This Site and All Sites That Inherit from It radio button.
Then select an option from the Site Master Page drop-down list.
Select the Reset Subsites to Inherit This Master check box if you want subsites of the current site to use the same master page.
Set the site to inherit the system master page by selecting the Inherit System Master Page from Parent of This Site radio button.
Or specify a different System Master Page by selecting the Specify a System Master Page for This Site and All Sites That Inherit from It radio button and selecting an option from the System Master Page drop-down list.
The system master is applied to system-based pages, such as library pages. You don't have to have the same master for the site pages and the system pages.
You can configure the site to inherit the alternate CSS of the parent, use the default SharePoint CSS, or use an alternate CSS. If you have a CSS attached to a custom master, you may not need an alternate CSS.
On the other hand, if you’re using the v4.master or the Night and Day master and you just want to apply different colors, spacing, or images, you can point to an alternate style sheet.
Inherit the alternate CSS from the parent site by selecting the Inherit Alternate CSS URL from Parent of This Site radio button.
Or specify SharePoint Foundation default CSS by selecting the Use Microsoft SharePoint Foundation Default Styles radio button, or specify an alternative CSS option by selecting the Specify a CSS File to Be Used by This Publishing Site and All Sites That Inherit from It radio button and browsing to an existing CSS using the Browse button.
Click OK to apply your changes.
If you just chose a site master, you need to click a publishing page to see the results.
If you don’t like the predefined SharePoint 2010 master pages, you can create your own custom master for your site.