My CSS isn't being applied.

var roomRequest = new XMLHttpRequest();
roomRequest.onreadystatechange = function () {
  if(roomRequest.readyState === 4 && roomRequest.status === 200) {
    var rooms = JSON.parse(roomRequest.responseText);
    var statusHTML = '<ul class="room">';
    for (var i=0; i<rooms.length; i += 1) {
      if (rooms[i].available === true) {
        statusHTML += '<li class="empty">';
      } else {
        statusHTML += '<li class="full">';
      }
      statusHTML += rooms[i].room;
      statusHTML += '</li>';
    }
    statusHTML += '</ul>';
    document.getElementById('roomList').innerHTML = statusHTML;
  }
};
roomRequest.open('GET', '../data/rooms.json');
roomRequest.send();