VolodinAS,
так?
#container{border:3px solid #000; }
#container2{width:49%;float:left;height:50px; border:3px solid #000;margin-left:5px; }
<div id="container">
<div style="width:100%; height:1px; clear:both;"></div>
<div id="container2">123</div>
<div id="container2">321</div>
<div style="width:100%; height:1px; clear:both;"></div>
</div>
<span style="position: relative;bottom: 75px;left: 0px;text-align: center;margin: 0% 25% 0% 25%;"><h1>Текст в контейнере поверх дивов.</h1></span>