function $(id){return document.getElementById(id);} 
function addEvent(obj, evType, fn, useCapture){ 
    if(obj.addEventListener){ 
        obj.addEventListener(evType, fn, useCapture); 
    }else if(obj.attachEvent){ 
        obj.attachEvent("on"+evType, fn); 
    }else{ 
        obj['on'+evType]=fn; 
    } 
} 
function removeEvent(obj, evType, fn, useCapture){ 
  if (obj.removeEventListener){ 
    obj.removeEventListener(evType, fn, useCapture); 
  } else if (obj.detachEvent){ 
    obj.detachEvent("on"+evType, fn); 
  } else { 
    obj['on'+evType]=function(){}; 
  } 


} 
function mostrar(e){ 
    var e=e || window.event; 
    var obj=e.srcElement || e.target; 
    alert(obj.id); 
} 


function getStyle(elemento, propiedadCss) {
  var valor = "";
  if(document.defaultView && document.defaultView.getComputedStyle){
    valor = document.defaultView.getComputedStyle(elemento, '').getPropertyValue(propiedadCss);
  }
  else if(elemento.currentStyle) {
    propiedadCss = propiedadCss.replace(/\-(\w)/g, function (strMatch, p1) {
      return p1.toUpperCase();
    });
    valor = elemento.currentStyle[propiedadCss];
  }
  return valor;
}