how do i add content to a TableCell using it's ID ?

how do i add content to a TableCell using it's ID ?

i have this table :


Code: <asp:Table ID="MainTable" runat="server" width="1025px">
<asp:TableRow >
<asp:TableCell ColumnSpan ="2"
BackColor="#4c4c4c">
<asp:Image ID="sitelogo"
imageurl="~/Images/cp.jpg"
runat="server"
AlternateText="Cli-Rest Logo" />
</asp:TableCell>
</asp:TableRow>
<asp:TableRow>
<asp:TableCell ColumnSpan=&q ...