cannot access form controls after using master page

Hi,

I have designed my website in Asp.net.

the aspx page contains <asp:content id="con1" runat="server"> and got the controls within the tags like <asp:label id ="lblxyz" runat="server">

when i go to code behind, I cannot access any controls. I get the error message when i write

lblxyz.Text = "this is it"

error message"lblxyz is not declared" It may be inaccessible due to its protection level.