.img{width:360px;height:360px;margin:0 auto;padding:0;position:relative;border:0} 
.iphone{ position:absolute;z-index:0;width:360px;height:360px} 
.iframe{ position:absolute;z-index:4;width:360px;height:360px} 
.imask{ position:absolute;z-index:3;width:360px;height:360px} 

.button_set {
    /*background-color: #4CAF50;  Green */
    border: none;
    color: white;
    padding: 20px 20px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 10px;
	border-radius: 30%;
}