Ken,
I have already removed line 26 from my current production environment's cutesoft_client/cuteeditor/template.aspx ...
21 <html>
22 <head>
23 <title>Untitled</title>
24 <meta name="GENERATOR" content="CuteEditor">
25 <base target="_blank" href="<%=Server.HtmlEncode(referrer)%>" />
26 <link type="text/css" rel="stylesheet" href='<%=CuteEditor.EditorUtility.ProcessWebPath(Context,Page,"Load.ashx?type=style&file=SyntaxHighlighter.css")%>' />
27 </head>
28 <body>
29 </body>
30 </html>
Removing this line does fix the secure/insecure mixed content warning problem, but it creates another problem... When the user tries to apply formatting to a highlighted section of content, the formatting is applied to the entire content block.
My assumption is that if you fix the CuteEditor.EditorUtility.ProcessWebPath() method to return a relative path rather than a full static URL, then the mixed content warning should go away.
-Tim