function lanzar(valor)
 {       
  if(window.XMLHttpRequest) {
   objXml = new XMLHttpRequest(); // Gecko (Firefox, Moz), KHTML (Konqueror, Safari), Opera
  } else if(window.ActiveXObject) {
   objXml = new ActiveXObject("Microsoft.XMLHTTP"); // Internet Explorer  
  }     
  
  objXml.open("GET", "tablero.asp?tipo="+valor , true); 
  //objXml.open("GET", "yo.html" , true); 
  objXml.onreadystatechange=function() {
     if (objXml.readyState==4) {                
          document.getElementById("tableros").innerHTML=objXml.responseText;
    }
   }               
  objXml.send(null);    
 }