.treeview .hitarea {
    background: url(/images/tree/expand_plusminus.gif) 0 -16px no-repeat;
    height: 18px;
    width: 18px;
    margin-left: -18px;
    float: left;
    cursor: pointer;
}
fix for IE6
* html .hitarea {
    display: inline;
    float:none;
}
.treeview .collapsable-hitarea {
    background: url(/images/tree/expand_plusminus.gif) 0 2px no-repeat;
}
.treeview li {
    list-style-type: none;
}