<style>
.clearfix {
    clear: both;
    margin-top: 9999px;
    margin-bottom: 100px;
    background-color: black;
    width: 10px;
    height: 10px;
}
.square {
    float: left;
    width: 49px;
    height: 49px;
}
.white {
    background-color: salmon;
    width: 100px;
    height: 100px;
}
.black {
    background-color: slateblue;
}
</style>
<div><div class="square white"></div><div class="clearfix"></div><div class="square black"></div></div>