html {
  /* background: url('../img/ceu.jpg') no-repeat center; */
  /* background: url('..//assets/fundo.png'); */
  background-image: url("http://averdadesobreofim.com.br/assets/imgs/fundo_home.jpg");
  
  background-repeat: no-repeat;
  /* background-size: 100%; */
  background-clip: content-box;
  background-attachment: fixed;
  background-size: cover;
  position: relative;
  display: flex;
}

.popup {
  /* border: 2px solid red; */
  width: 300px;
  height: 200px;
  position: fixed;
  top: 50%;
  position: fixed;
  margin-top: -100px;
  left: 50%;
  margin-left: -150px;
}
.popup img {
  width: 100%;
}