[SharePoint 2010]: Managing People & Group at Site Collection Level

Important If you remove the user from the All People group, all the user's permissions to this Site Collection are removed. Before you remove the user's permissions and re-add them, note the user's permissions. To do this, on the Site Actions menu, click Site Permissions, and then click Check Permissions.

The All People group is hidden in SharePoint 2010. However, to access this group, you can modify the following URL in the browser:

<Site URL>/_layouts/people.aspx?MembershipGroupId=0

For example, the URL will resemble the following:

https://contoso.com/sites/<SpecificSiteName>/_layouts/people.aspx?MembershipGroupId=0

If you remove the user from this group, this also removes the user from the userInfo table in the Microsoft SQL Server database. When you re-add the user, the user's information is updated in this table.

For instructions about how to grant users access to a Site, visit the following website:

Roadmap: Grant permissions for a site