#main {width:100%;overflow:hidden;}

/* .main_visual {width:100%;height:860px;background:url(http://centreville-theopera.co.kr/images/main_img.jpg) no-repeat center;background-size:cover;position:relative;} */
.main_visual {width:100%;height:100vh;background:url(http://centreville-theopera.co.kr/images/main_img.jpg) no-repeat center;background-size:cover;position:relative;}