table.tablesorter thead tr .header {
    background-image: url(../images/bg.gif);
    background-repeat: no-repeat;
    background-position: center right;
    cursor: pointer;
    height: 40px;
}

table.tablesorter thead tr .headerSortUp {
    background-image: url(../images/asc.gif);
}
table.tablesorter thead tr .headerSortDown {
    background-image: url(../images/desc.gif);
}
table.tablesorter th {
    cursor: pointer;
}
table.tablesorter thead th:hover {
    background-color: #dad8d8;
}