function initMain(){
  var bb = document.getElementById('by-brand-btn');
  var bc = document.getElementById('by-category-btn');
  var bbh = document.getElementById('by-brand-holder');
  var bch = document.getElementById('by-category-holder');
  if (bb && bc && bbh && bch){
    bb.onclick = function(){
      bch.style.display = 'none';
      bbh.style.display = 'block';
    }
    bc.onclick = function(){
      bch.style.display = 'block';
      bbh.style.display = 'none';
    }    
  }
}
if (window.addEventListener){
	window.addEventListener("load", initMain, false);
}
else if (window.attachEvent && !window.opera){
	window.attachEvent("onload", initMain);
	}