body{
  background-image: url('blog/christmas_black.png');
  background-attachment: fixed;
  background-repeat: repeat;
  overflow: auto;
}


p,h1,h2,h3,h4,h5,h6{
  color:whitesmoke;
}

hr {
  border-color:whitesmoke;
}

img {
  height:200px;
}

.main_section{
  background-color: #3C4142;
  width: 840px;
  margin: auto;
  box-sizing:border-box; /*包括padding和border*/
  padding: 10px;
  margin-top:30px;
  margin-bottom:30px;
}