Cannot applied CSS in <Col>

 <MAC:Panel ID="pnlEmployeeDetail" runat="server" GroupingText="EmployeeDetail">
                        <table class="defaultTable">
 
                            <tr>
                                <td style="width: 50%">
                                    <table class="defaultTable">
 
                                        <colgroup>
                                          <col class="formLabel"/> 
                                          <col class="topPadding"/>
                                          <col />
                                        </colgroup>
 
 
 
                                        <tr>
                                            <td>
                                                <MAC:Literal ID="Literal3" runat="server" Text="EmployeeNo"></MAC:Literal>
                                            </td>
                                            <td>&nbsp;:&nbsp;
                                            </td>
                                            <td>
                                                <%# Eval("EmployeeNo") %>
                                            </td>
                                        </tr> 
                                 ......................................
 
                                               CSS
========================================================================================================
.defaultTable .formLabel
{
    width: 150px;
 
    padding-top: 3px;
    vertical-align: top;
    height: 22px;
 
 
}
 
.defaultTable .topPadding
{
    vertical-align: top;
    padding-top: 3px;
    width: 2px;
}