.tb_org th {

            background-color: #;

            color: #ffffff;

        }

        .tb_org {

            border-right: 1px solid silver;

            border-bottom: 1px solid silver;

            border-collapse: collapse;

            width: 440px;

            overflow-x: auto;

           text-align:center;

        }

            .tb_org thead td {

                border-right: 1px solid;

                text-align: center;

                background-color: #70c3d5;

                color: #ffffff;

            }

            .tb_org tr:hover {

                background-color: #f2eeee;

            }

            .tb_org tbody td {

                border-left: 1px solid silver;

                border-top: 1px solid silver;

            }

 <fieldset style="overflow-y:auto;">

                <table id="tb_org" class="tb_org">

                    <thead>

                        <tr><th>机构名称</th><th>预算金额</th></tr>

                    </thead>

                    <tbody></tbody>

                </table>

            </fieldset>