Before users can use the Search Center, you must specify which users and groups can access the site. After you grant users and groups permission to the Search Center site, they can view standard and federated search results on content they have permission to view. Users who have just received permissions to view site content results might not see results until after the next crawl.
As new people join your organization over time, it will be necessary for you to add them to the permissions list. Consider programmatically automating this process to ensure that everyone in your organization has access to the site at all times.
What do you want to do?
Grant users access to the Search Center site
We recommend that you use SharePoint groups whenever possible to manage Search Center site access. You can add users to one or more of the group-based permission levels provided with the Search Center site, or create a new group with a custom permission level. When you have a large number of users to add or maintain, you can save time by programmatically automating the process.
On the Search Center site, click the Site Actions menu , and then click click Site Settings.
On the Site Settings page, under Users and Permissions, click People and Groups.
On the People and Groups page, on the Quick Launch, click Groups to display all of the existing groups and their descriptions.
Under Groups, click the name of the group in which you want to add users.
On the menu bar, click the arrow next to the New button, and then click Add Users.
In the Users/Groups box, type the name of the user you want to add. To add multiple users, type their names separated by a semicolon.
Note: If your server is configured for domain-based authentication, you must include the domain name in front of each user name or alias in the format DOMAIN\alias. Click the Check Names icon to make sure that each name in the list is resolved.
Note: Individual users and groups can have different permission levels for different securable objects. For example, you can assign different users and groups different permission levels for a specific site, list, library, folder within a list or library, list item, or document.
Learn more about users, groups, and permissions
To learn more about the administration of users and groups in Microsoft SharePoint Server 2010, see "Control user access and permissions" in the Help for SharePoint Server 2010. For more information about programatically automating adding users, look for more information on Windows SharePoint Services Developer Center on MSDN.