*{
    margin: 0;
    padding: 0;
}
li{
    list-style: none;
}
a{
    text-decoration: none;
}

.chang_bg{
     width: 1200px;
     height: 800px;
     position: absolute;   

     top: 46px;
     left: 50%;
    margin-left: -600px;
}

.chang_nav{
    width: 1087px;
    height: 566px;
    
    position: absolute;
    top: 163px;
    left: 50%;
    margin-left: -533px;
 
   
}