control error in master page when build solution

See more:

ASP.NET

I use

<div id="logoff" runat="server">
                                    <a class="logoff" id="loggmeof" href="#">LogOff</a>
                                </div>

in master page , and in page_load , if give
logoff.Visible = false;


and when i build in visual studio 2008 , it gives error for logoff not found

then when i comment it out , it says build successfull