function showContent(showId, aId) {
  document.getElementById(lastShowId).style.display = "none";
  document.getElementById(showId).style.display = "block";
  lastShowId = showId;
  if (lasta) {
    lasta.className = "";
  }
  lasta = document.getElementById(aId);
  lasta.className = "on";
}
var lastShowId = "home_welcome_content";
var lasta = null;