Restricting access to SharePoint master pages

Master pages are a powerful way to design and brand SharePoint sites, so you may not want to allow everyone in your organization to customize these files. For starters, they could potentially break multiple SharePoint pages or sites if they delete a content placeholder control or script from a master page (instead of hiding it). They might customize their sites’ master pages to the point where they are no longer recognizable as belonging to the corporate intranet, which could affect a user’s experience when visiting that site. Or, you may simply want to prevent any user from creating new master pages because these pages will need to be maintained and updated, which adds to the overall maintenance costs of your SharePoint implementation.
By default, only Site Collection Administrators, members of the Designers group, and members of the Site Owners group can open a SharePoint site with SharePoint Designer 2010 and, if they like, customize the default master pages. To further restrict who can customize master pages in SharePoint Designer 2010, use the SharePoint Designer Settings page, located on the Site Settings page for the site collection as well as in Central Administration.
There are two pages so that you can specify the level (web application or site collection) and the types of users (site collection administrators or designers and owners) to be restricted in SharePoint Designer 2010, as shown here.

SharePoint Designer Settings page	Types of sites and users affected
Central Administration	Restricts SharePoint Designer 2010 for Site Collection Administrators at the web application level, which includes all site collections and sites in that web application.
Site Collection Administration	Restricts SharePoint Designer 2010 for all Site Owners and Designers at the site collection level, which includes all sites within the collection. Note These settings are dependent on SharePoint Designer 2010 first being enabled in Central Administration.

To prevent users from customizing master pages on your SharePoint sites, you can uncheck the Enable Customizing Master Pages and Layout Pages on one or both of the SharePoint Designer Settings pages. When this option is disabled, users will no longer see the Master Pages or Page Layouts links in the Navigation pane of SharePoint Designer.

Note Page Layouts only display for publishing-enabled pages in SharePoint Designer 2010.
In addition to disabling master pages and page layouts, you can use the SharePoint Designer Settings page to disable the site URL hierarchy, which hides the All Files option in the Navigation pane. You can also prevent pages from being detached from their site definition by disabling the Edit File in Advanced Mode for all site pages. Lastly, you can completely disable SharePoint Designer 2010 so that it can’t open and customize your SharePoint sites or portions of those sites.
In sum, use the SharePoint Designer Settings page to control who can create and customize the default master pages in SharePoint 2010 to best support your corporate design and brand.