tree.css

div.one-tree-forest {
    text-align: center;
    width: 100%;
    position: relative;
}

div.one-tree-forest ul {
    position: relative;
    display: inline-block;
    zoom: 1;
    *display: inline;
    min-width: 75px;
    height: 75px;
    white-space: nowrap;
    clear: both;
    position: relative;
    /*background-color: rgba(0, 0, 255, .1);*/
    padding: 0px 14px;
    margin: 100px 10px 0px 10px;
    top: -100px;
}

div.one-tree-forest li {
    position: relative;
    display: block;
    float: left;
    white-space: nowrap;
    margin: 20px 0px;
    /*background-color: rgba(255, 0, 0, .1);*/
}

/**/ div.tree-node {
    width: 100px;
    height: 100px;
    margin: auto;
    border: solid 1px #000;
    background-color: #DDD;
    border-radius: 10px;
    border: solid 1px black;
    text-align: center;
    line-height: 100px;
}

div.one-tree-forest li.tree-drop-zone div.tree-node {
    background-color: #EEE;
    border-radius: 5px;
    border: dashed 4px #999;
}

div.one-tree-forest div.tree-line {
    position: absolute;
    background-color: #000;
}

div.one-tree-forest div.tree-node-top, div.one-tree-forest div.tree-node-bottom {
    left: 50%;
    width: 1px;
}

div.one-tree-forest div.tree-branch-horizontal {
    height: 1px;
}