<style>
.container {
    overflow:auto;
}
.sidebyside {
    float:left;
    width:100px;
    height:100px;
    border-style:solid;
    margin:5px;
}
.belowdiv {
    width:300px;
    height:100px;
    border-style:solid;
    margin:5px;
}
</style>

<div class="container">
    <div class="sidebyside">div0</div>
    <div class="sidebyside">div1</div>
    <div class="sidebyside">div2</div>
    <div class="sidebyside">div3</div>
    <div class="sidebyside">div4</div>
</div>
<div class="belowdiv">div5</div>
<div class="belowdiv">div6</div>
<div class="belowdiv">div7</div>
<div class="belowdiv">div8</div>
<div class="belowdiv">div9</div>