.sortable .sorttable_img:before {
    content: "\00a0\00a0\00a0";
    display:inline;
    background: url("no_sort.gif");
    cursor: pointer;
    margin-left: 0.25em;
}
.sortable .sorttable_img.asc_sort:before {
    background: url("asc_sort.gif");
}
.sortable .sorttable_img.desc_sort:before {
    background: url("desc_sort.gif");
}