navigator.userAgent
function validB(){
 var u_agent = navigator.userAgent;

 var B_name="Failed to identify the browser";
 if(u_agent.indexOf("Firefox")>-1){
     B_name="Firefox";
 }else if(u_agent.indexOf("Chrome")>-1){
     B_name="Chrome";
 }else if(u_agent.indexOf("MSIE")>-1&&u_agent.indexOf("Trident")>-1){
     B_name="IE(8-10)";  
  }    document.write("B_name:"+B_name+"<br>");
    document.write("u_agent:"+u_agent+"<br>"); }