w3c (validation) for Imagebutton in aspx page having (there is no attribute "ID" and "runat")

Hi,
I am checking the W3C (validation) for website.
But some of page cant check with URL input coz of some of them are not public page and has to login with password.
So I use direct input for validation of my page and I used XHTML 1.0 Transitional for validation.
But I have these following errors and cant find out in google for these error detail.
Please, can anyone give me any idea for this. Thanks in advanced.
Line 15, Column 67: there is no attribute "runat"
<asp:ImageButton ID="imgbNominator" runat="server"
                            ImageUrl="~/images/Content/nominator_menu_off.jpg"
&n ...