liborio,
Try set the following property to true then try again.
Editor.UseFontTags Property
Font tags are now deprecated, meaning that they aren't used any more and will cause validation errors. Many legacy pages still contain style information in font tags. By default Cute Editor converts font tags to span tags. <font face="times" size="4" color="#ffffff">your text</font> would be replaced with <span style="font-family: times, serif; font-size: 110%; color:#ffffff">your text</span> If you still want to use font tags, you can set this property to true.
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