Did you mean this:

<CE:Editor id="Editor1" Width="100%" runat="server" ></CE:Editor>

I have done this already and it does not work. This is my code:

<CE:Editor Width="100%" DisableAutoFormatting="true" EnableContextMenu="false" id="txtContent" Text="" runat="server" AutoConfigure="Full"  AutoParseClasses="false"></CE:Editor>

Could it be caused by the <%asp%> code on the web page template file, that pulls in the editor, has width="100%" too?

So stuck!.