<li class="block">
<div class="desc"></div>
<img src="img/img-1.jpg" alt="Image 1">
</li>.block {
position: relative;
}
.desc {
position: absolute;
display: none;
top: 0;
left: 0;
bottom: 0;
right: 0;
}
.block:hover .desc {
display: block;
}