This is strange.

That page you linked renders correctly, but my example does not. 

 

I have this version of Opera - it is a current beta:

Opera/9.50 (Windows NT 5.1; U; en) 

 

I put the example I mentioned earlier to publicly accessible site - and it renders incorrectly - http://trupik.aspweb.cz/default2.aspx

 

Also in this example, when I click the Insert Image button I get this error:

 

Server Error in '/' Application.
Input string was not in a correct format.

 

[FormatException: Input string was not in a correct format.]
   System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +2725283
   System.Number.ParseDouble(String value, NumberStyles options, NumberFormatInfo numfmt) +113
   System.Double.Parse(String s, NumberStyles style, NumberFormatInfo info) +188
   System.Convert.ToDouble(String value) +68
   CuteEditor.UploaderBase.get_IsBrowserSupportUploadScript() +1354
   CuteEditor.UploaderBase.OnPreRender(EventArgs e) +20
   System.Web.UI.Control.PreRenderRecursiveInternal() +77
   System.Web.UI.Control.PreRenderRecursiveInternal() +161
   System.Web.UI.Control.PreRenderRecursiveInternal() +161
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1360

 

But again - the page you linked does not throw this exception (in the same browser).