<asp:TextBox ID="txtCCEmail" runat="server" TextMode="MultiLine" Height="50" CssClass="textbox"
Width="250"></asp:TextBox><br />
<ajaxToolkit:TextBoxWatermarkExtender ID="TextBoxWatermarkExtender3" runat="server"
TargetControlID="txtCCEmail" WatermarkText="sample1@yourcompany.com; sample2@yourcompany.com;"
WatermarkCssClass="watermarked">
</ajaxToolkit:TextBoxWatermarkExtender>