Installed ajax control toolkit -issues w/ 2010

I installed the ajax control toolkit into my vs 2010 - I did the change it said to do the web.config, but that line - didnt work. I moved that line

<%@RegisterTagPrefix="asp"Namespace="AjaxControlToolkit"Assembly="AjaxControlToolkit"%>

over to the default.aspx page, and it appeared correctly (the <% and %> were yellow), but I still didnt see anything in the toolbx listing.  I added the

<asp:ToolkitScriptManagerrunat="Server"/><asp:TextBox       ID="txtComments"       TextMode="MultiLine"       Columns="60"        Rows="8"       runat="server"/><asp:HtmlEditorExtender       TargetControlID="txtComments"       runat="server"/>

and the text box showed up one time - and then when I reloaded the app, the control claimed to be undefined.  I have vs 2010, 10.0.40219.1 sp1rel   and .net framework version 4.5.50709 sp1rel.

Anyone have any idea what I am doing wrong?  Thanks

DonnieS