you can use style
<td colspan="2">
<div style="float:left; width:80px"><asp:Label ID="Label6" runat="server" Text="Label"></asp:Label></div>
<div style="float: right; width:100px">
<asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
</div>
<div style="clear:both"></div>
</td>