.header {
    min-height:300px;
    top:0px;
    left:0px;
    right:0px;
    z-index:1000;
    position:fixed;
}
.nav_menu {
    text-align: center;
}
#Menu1_list {
    display: none;
    text-align:left;
}
.customClass1 {
    display: inline-block;
}
@media only screen and (min-width : 768px) {
    #Menu1_list {
        display: block;
    }
    .customClass1 {
        display: none;
    }
    .header {
        min-height: 58px;
        width:100%;
    }
}
@media only screen and (min-width : 1024px) {
    .header {
        min-height: 58px;
        width:100%;
    }
}