.nav-correct {
  margin-top: 100px;
}
@media (max-width: 768px) {
  .nav-correct {
    margin-top: 50px;
  }
}

.index-picture {
  background-image: url(../images/index-picture.jpg);
  background-size: cover;
  height: 500px;
  width: 100%;
  z-index: -1;
  position: absolute;
}

@media (max-width: 768px) {
  .index-picture {
    height: 300px;
  }
}

.index-introduce {
  height: 500px;
  z-index: 1;
}

@media (max-width: 768px) {
  .index-introduce {
    height: 250px;
  }
}

.introduce {
  color: white;
  background-color: rgba(0,0,0,0.5);
  height: 300px;
  margin-top: 100px;
}

@media (max-width: 768px) {
  .introduce {
    height: 200px;
    margin-top: 50px;
  }
}

footer {
  color: white;
  margin-left: -15px;
  margin-right: -15px;
}

.index-post-img {
  width: 40%;
  margin-right: 2%;	
}