.fl {width: 100%;}
.fl .bk {float: left;}

.bk:nth-child(1){ position:relative; width:300px; height:300px; background-color:#066;}
.bk:nth-child(2){ position:relative; width:300px; height:300px; background-color:#06F;}
.bk:nth-child(3){ position:relative; width:300px; height:300px; background-color:#C30;}

<div class="fl">
    <div class="bk">1</div>
    <div class="bk">2</div>
    <div class="bk">3</div>
</div>