.post309-h2-blue {
  color: white;
  background-color: blue;
  font-size: 130%;
  padding: 10px;
}

@media screen and (max-width: 768px) {

  .post309-img-size img {
    width: 100%;
    height: auto;
  }

  .post309-img-size2 img {
    width: 100%;
    aspect-ratio: 14/2;
  }

}