Jan,
With the above style sheet, you should get the "verdana" when your mouse cursor is in the editor area.
I am use the following code to test. If you still have problems, please try it:
<%@ Page Language="C#" %>
<%@ Register TagPrefix="CE" Namespace="CuteEditor" Assembly="CuteEditor" %>
<html>
<body>
<form runat="server" ID="Form1">
<CE:Editor id="Editor1" EditorWysiwygModeCss="EditorStyles.css" runat="server" ></CE:Editor>
</form>
</body>
</html>
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