function showBranch(branch,button,n) {
   var objBranch = document.getElementById(branch).style;
   var objButton = document.getElementById(button);
   n++;
     for (x=1;n>x;x++) {
		  var z = "link"+x;
		  document.getElementById(z).className="back";
	  }
	  objButton.className="current";
      for (x=1;n>x;x++) {
		  var z = "branch"+x;
      	  document.getElementById(z).style.display="none";
	  }
	  objBranch.display="block";
}