I have come up with a customized admin panel and basically don't want it to be visible unless the user is signed in.  I tried incorporating your usercontrol suggestion I'm getting weird results.

Here's what the menu looks like when the user is signed in:  http://bit.ly/9ThUbL

The following is my usercontrol code:

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="AdminOnlyLinks.ascx.cs" ClassName="AdminOnlyLinks.ascx" Inherits="Controls_AdminOnlyLinks" %>
<div id="admin">
<div id="buttons">
<portal:LogoutLink id="LogoutLink" runat="server" CssClass="logoff" RenderAsListItem="false" />
<portal:SiteMapLink id="SiteMapLink1" runat="server" />
<a href="/Admin/ContentCatalog.aspx">Content Manager</a>
<a href="/Admin/PageTree.aspx">Add/Edit Pages</a>
<asp:ContentPlaceHolder ID="pageEditContent" runat="server"></asp:ContentPlaceHolder>
</div>
<a id="show_hide" class="arrow down" href="javascript:toggleVisibility()"></a>
</div>

However, when I insert  <cc1:AdminOnlyLinks id="hiddenlinks1" runat="server" /> , I get the following: http://bit.ly/abpQNZ

I get an error in the log:

 

2010-03-26 12:16:42,268 ERROR mojoPortal.Web.mojoBasePage - Error setting master page. Will try setting to default skin.en-US - 131.156.71.164
System.Web.HttpParseException: Unknown server tag 'cc1:AdminOnlyLinks'. ---> System.Web.HttpParseException: Unknown server tag 'cc1:AdminOnlyLinks'. ---> System.Web.HttpException: Unknown server tag 'cc1:AdminOnlyLinks'.

I added a directive to the layout.master as like so:

<%@ Register Src="~/Controls/Custom/AdminOnlyLinks.ascx" TagName="AdminOnlyLinks" TagPrefix="cc1" %>

Here's the code-behind file just in case:

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using mojoPortal.Web;
using mojoPortal.Web.UI;
using mojoPortal.Web.Framework;
using mojoPortal.Business;
using mojoPortal.Business.WebHelpers;

public partial class Controls_AdminOnlyLinks : System.Web.UI.UserControl
{

protected void Page_Load(object sender, EventArgs e)
{
PageSettings currentPageSettings = CacheHelper.GetCurrentPage();
SiteSettings siteSettings = CacheHelper.GetSiteSettings(currentPageSettings.SiteId);
string siteRoot = WebUtils.GetSiteRoot();

if (
(WebUser.IsAdminOrContentAdminOrRoleAdmin)
|| (
(WebConfigSettings.UseRelatedSiteMode)
&& (WebUser.IsInRoles(siteSettings.SiteRootEditRoles))
)
)
{
this.Visible = true;
}

else
{ this.Visible = false; }
}
}

Removed the ContentPlaceHolder like you suggested - didn't help.  This is what I have in the log:

2010-03-29 10:17:04,033 ERROR mojoPortal.Web.mojoBasePage - Error setting master page. Will try setting to default skin.en-US - 131.156.71.164
System.Web.HttpParseException: ContentPlaceHolder can only be used in .master files. ---> System.Web.HttpParseException: ContentPlaceHolder can only be used in .master files. ---> System.Web.HttpException: ContentPlaceHolder can only be used in .master files.
at System.Web.UI.WebControls.ContentPlaceHolderBuilder.Init(TemplateParser parser, ControlBuilder parentBuilder, Type type, String tagName, String ID, IDictionary attribs)
at System.Web.UI.ControlBuilder.CreateBuilderFromType(TemplateParser parser, ControlBuilder parentBuilder, Type type, String tagName, String id, IDictionary attribs, Int32 line, String sourceFileName)
at System.Web.UI.ControlBuilder.CreateChildBuilder(String filter, String tagName, IDictionary attribs, TemplateParser parser, ControlBuilder parentBuilder, String id, Int32 line, VirtualPath virtualPath, Type& childType, Boolean defaultProperty)
at System.Web.UI.TemplateParser.ProcessBeginTag(Match match, String inputText)
at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding)
--- End of inner exception stack trace ---
at System.Web.UI.TemplateParser.ProcessException(Exception ex)
at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding)
at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding)
--- End of inner exception stack trace ---
at System.Web.UI.TemplateParser.ProcessException(Exception ex)
at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding)
at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding)
at System.Web.UI.TemplateParser.ParseFile(String physicalPath, VirtualPath virtualPath)
at System.Web.UI.TemplateParser.ParseInternal()
at System.Web.UI.TemplateParser.Parse()
at System.Web.Compilation.BaseTemplateBuildProvider.get_CodeCompilerType()
at System.Web.Compilation.BuildProvider.GetCompilerTypeFromBuildProvider(BuildProvider buildProvider)
at System.Web.Compilation.BuildProvidersCompiler.ProcessBuildProviders()
at System.Web.Compilation.BuildProvidersCompiler.PerformBuild()
at System.Web.Compilation.BuildManager.CompileWebFile(VirtualPath virtualPath)
at System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile)
at System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile)
at System.Web.UI.MasterPage.CreateMaster(TemplateControl owner, HttpContext context, VirtualPath masterPageFile, IDictionary contentTemplateCollection)
at System.Web.UI.Page.get_Master()
at mojoPortal.Web.mojoBasePage.SetupMasterPage()
at mojoPortal.Web.mojoBasePage.OnPreInit(EventArgs e)
2010-03-29 10:17:11,500 ERROR mojoPortal.Web.mojoBasePage - Error setting master page. Will try setting to default skin.en-US - 131.156.71.164
System.Web.HttpParseException: ContentPlaceHolder can only be used in .master files. ---> System.Web.HttpParseException: ContentPlaceHolder can only be used in .master files. ---> System.Web.HttpException: ContentPlaceHolder can only be used in .master files.
at System.Web.UI.WebControls.ContentPlaceHolderBuilder.Init(TemplateParser parser, ControlBuilder parentBuilder, Type type, String tagName, String ID, IDictionary attribs)
at System.Web.UI.ControlBuilder.CreateBuilderFromType(TemplateParser parser, ControlBuilder parentBuilder, Type type, String tagName, String id, IDictionary attribs, Int32 line, String sourceFileName)
at System.Web.UI.ControlBuilder.CreateChildBuilder(String filter, String tagName, IDictionary attribs, TemplateParser parser, ControlBuilder parentBuilder, String id, Int32 line, VirtualPath virtualPath, Type& childType, Boolean defaultProperty)
at System.Web.UI.TemplateParser.ProcessBeginTag(Match match, String inputText)
at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding)
--- End of inner exception stack trace ---
at System.Web.UI.TemplateParser.ProcessException(Exception ex)
at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding)
at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding)
--- End of inner exception stack trace ---
at System.Web.UI.TemplateParser.ProcessException(Exception ex)
at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding)
at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding)
at System.Web.UI.TemplateParser.ParseFile(String physicalPath, VirtualPath virtualPath)
at System.Web.UI.TemplateParser.ParseInternal()
at System.Web.UI.TemplateParser.Parse()
at System.Web.Compilation.BaseTemplateBuildProvider.get_CodeCompilerType()
at System.Web.Compilation.BuildProvider.GetCompilerTypeFromBuildProvider(BuildProvider buildProvider)
at System.Web.Compilation.BuildProvidersCompiler.ProcessBuildProviders()
at System.Web.Compilation.BuildProvidersCompiler.PerformBuild()
at System.Web.Compilation.BuildManager.CompileWebFile(VirtualPath virtualPath)
at System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile)
at System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile)
at System.Web.UI.MasterPage.CreateMaster(TemplateControl owner, HttpContext context, VirtualPath masterPageFile, IDictionary contentTemplateCollection)
at System.Web.UI.Page.get_Master()
at mojoPortal.Web.mojoBasePage.SetupMasterPage()
at mojoPortal.Web.mojoBasePage.OnPreInit(EventArgs e)

Thanks for the complements :)

Another important detail is that if I do take out " <asp:ContentPlaceHolder ID="pageEditContent" runat="server"></asp:ContentPlaceHolder>" and place it in the AdminOnlyLinks control, then mojoPortal complaints about the lack of pageEditContent in the layout.master.

So I how do I make sure that AdminOnlyLinks contains pageEditContent w/o causing any problems here?