.cf:before,

.cf:after
{
    content: " ";
    display: table;
}

.cf:after
{
    clear: both;
}
.gallery_container
{
    max-width: 780px;
    background: #f0f0f0;
    padding: 10px;
}

.gallery
{
    width: 100%;   
}

.gallery_item
{
    float: left;
    background: #fff;
    margin: .5%;
    padding: .5%;
    padding-bottom: 1%;
    box-shadow: 1px 1px 3px rgba(0,0,0,.2);
}

.gallery_item img
{
    width: 100%;
}