function createMessageContainer(classname) {
  messageContainer = document.createElement('div');
  messageContainer.className = classname;
  messageContainer.innerHTML = 'DEBUG';
  messageContainer.style.background = 'yellow';
  messageContainer.style.position = 'absolute';
  messageContainer.style.top = '0px';
  document.body.appendChild(messageContainer);
}
Creates message container element
@function
@param {string} classname - Container classname.