Scenario:

Client wanted to hide the ribbon from everyone except admin.

Solution:

Open your SharePoint master page

Add the following style in head section

 style type="text/css">
#s4-ribbonrow { display : none; }
</style>

Now find the start of the "s4-ribbonrow" tag and add following this:

<Sharepoint:SPSecurityTrimmedControl ID="SPSecurityTrimmedControl2" runat="server" PermissionsString="AddAndCustomizePages">

<style type="text/css">

#s4-ribbonrow { display : block; }

</script>
</Sharepoint:SPSecurityTrimmedControl>


Save the new master page and publish it.