Please check the following code. After I loaded the rtf, I noticed that the font size came out wrong. The font size in html mode was 10px but it displayed as 8px on screen.
string rtf1 = @"{\rtf1\ansi\ansicpg1252\deff0\deflang1033{\fonttbl{\f0\fswiss\fcharset0 arial;}}{\colortbl ;\red0\green0\blue0;}\viewkind4\uc1\pard\qj\cf1\f0\fs20 test1234567890test\par}";
CuteEditor1.LoadRTF(rtf1);