Hiding the Ribbon :
In your master page, find the SharePoint ribbon by looking for the line of code that begins with . Place the SPSecurityTrimmedControl code around your ribbon to conditionally hide it based on user permissions. In my example, i've hidden the ribbon from any user who doesn't have the ManagePermissions ability, which is going to be almost any user short of a site administrator.
<SharePoint:SPSecurityTrimmedControl PermissionsString="ManagePermissions" runat="server">
<div id="s4-ribbonrow" class="s4-pr s4-ribbonrowhidetitle">
<!-- Ribbon code appears here... -->