function prepareTargetBlank(){
   var className = 'popup';
   var className2 = 'popupindex';
   var as = document.getElementsByTagName('a');
   for(i=0;i<as.length;i++){
      var a = as[i];
      r=new RegExp("(^| )"+className+"($| )");
      r2=new RegExp("(^| )"+className2+"($| )");
      if(r.test(a.className)){
         a.onclick = function(){
            window.open(this.href, a.className, "width=800,height=600,scrollbars=yes,resizable=yes,toolbar=yes");
            return false;
         }
      }
      if(r2.test(a.className)){
         a.onclick = function(){
         	var arriba=(screen.availHeight - 550)/2;
			var izquierda=(screen.availWidth - 700)/2;
            window.open(this.href, "login", "width=600,height=410,top=" + arriba + ",left=" + izquierda + ",scrollbars=yes,resizable=yes,toolbar=yes, status=yes, location=yes");
            return false;
         }
      }
    }
}
   
window.onload = prepareTargetBlank;