initClientlist = function() {
  var clients = document.getElementsByClassName("client");
  for (var i = 0, client; client = clients[i]; i++)  {
    client.onmouseover = function() {
      this.className = "client hover";
    }
    client.onmouseout = function() {
      this.className = "client";
    }
  }
}

    addEvent(window,"load",initClientlist);