.img_item{
  width: 70%;
  height: auto;
  margin: 100px 15%;
}

@media screen and (max-width: 768px) {
  .img_item{
    width: 95%;
    height: auto;
    margin: 20px 2.5%;
  }
  .small_blank_space{
    width: 100%;
    height: 30px;
  }
}