<script> 
var system ={}; 
    var p = navigator.platform;      
    system.win = p.indexOf("Win") == 0; 
    system.mac = p.indexOf("Mac") == 0; 
    system.x11 = (p == "X11") || (p.indexOf("Linux") == 0);    
    if(system.win||system.mac||system.xll){
        document.write("<p>PC</p>");
    }else{  
        document.write("<p>Mobile</p>");
    }
</script>