To hide master page content form content page, we can hide control
1: from Server
2: from Client
1:Server side or from Content Page, button click or some other event
Panel p= Master.FindControl("pnlPanel") as Panel;
if (p != null)
{
p.Visible = false;
}
2: from Client
<input id="Button2" type="button" value="From Client" onclick="hide();" />
<script >
function hide() {
document.getElementById("pnlPanel").style.display = 'none';
}
</script>