How To Hide Ribbon From Visitors in SharePoint 2010

•       Open your SharePoint master page

•       Locate this line:

    <div id="s4-ribbonrow" class="s4-pr s4-ribbonrowhidetitle">

•       Change it to: <div id="s4-ribbonrow" class="s4-pr s4-ribbonrowhidetitle" style="display:none">

•       Now find the end of the “s4-ribbonrow” tag and add following block right after it:

<Sharepoint:SPSecurityTrimmedControl ID="SPSecurityTrimmedControl2" runat="server" PermissionsString="AddAndCustomizePages">    <script type="text/javascript">        document.getElementById("s4-ribbonrow").style.display = "block";
    script>
Sharepoint:SPSecurityTrimmedControl>

•       Save the new master page and publish it.