header {
height: 100vh;
min-height: 600px;
display: flex;
flex-direction: column;
justify-content: center;
}header {
height: 100vh;
min-height: 600px;
position:relative
}
.container-fluid {
left:0;
width:100%;
position: absolute;
top: 50%;
transform: translateY(-50%);
}
var $html = $('html');
var lockedClass = namespacify('is-locked');
$html.addClass(lockedClass);<html class="remodal-is-locked">overflow: hidden