How to make Object1 invisible from C#

Hi,
I am trying to find a way to make Object1 invisible in code behind. I succed to do it for a1 but not for the Object1 even that I put the runat="server" tag to the Object1 ?
a1.Visible = false; //Show Panel Object1.Visible = false; // Object1 is not found ? <a ID="a1" runat="server" href="<%#setHopLink1a%>"> <img ID="AdvImage1" runat="server" alt="" src="<%#setSrc1%>" style="border: none" height="<%#setHeightImage1%>" width="<%#setWidthImage1%>" /></a> <object runat="server" ID="Object1" align="middle" classid="<%#setClassID1%>" ...