.picturebox-left {
    text-align: center;
    float: left;
    clear: left;
    margin-right: 10px;
    background: #cbcbcb;
    padding: 5px;
}
.picturebox-right {
    text-align: center;
    float: right;
    clear: right;
    margin-left: 10px;
    background: #cbcbcb;
    padding: 5px;
}