.box03{
-js-display: flex;
display: -webkit-flex;
display: -moz-flex;
display: -ms-flex;
display: -o-flex;
display: flex;
flex-wrap: wrap;
-webkit-justify-content: space-between;
justify-content: space-between;
width:  100%;
margin: 0;
position:relative;
}

.box03 li{
width: 31.5%;
margin-bottom: 15px;
}

.youtubeBox {
margin: 0 auto 30px auto;
text-align: center;
}

@media only screen and (max-width: 751px) {
.box03 li{
width: 48.5%;
}

.youtubeBox {
position: relative;
width: 100%;
padding-top: 56.25%;
}

.youtubeBox iframe {
position: absolute;
top: 0;
right: 0;
width: 100% !important;
height: 100% !important;
}
}