This will solve your problem
<table class="style5">
<tr>
<td>
Month:</td>
<td class="style6">
<asp:DropDownList ID="Ddlmonth1" runat="server" Height="24px"
style="margin-left: 0px" Width="115px"/>
</td>
<td>
<asp:CheckBox ID="CheckBox1" runat="server" />
</td>
</tr>
<tr>
<td>
Year</td>
<td class="style6">
<asp:DropDownList ID="DropDownList4" runat="server" Width="115px" Height="24px"/>