in the galleries/grid_fullsize/css/common.css file, you added a float: left; property to the ".pg-gf .title" selector that is causing the problem. Change the ".pg-gf .title" selector to:
.pg-gf .title {
width: 600px;
margin: 0 auto;
background-color: #474747;
padding: 10px;
border: solid 1px #000;
border-top: none;
border-bottom: none;
/*float:left;*/
margin-left:46px;
}