RadEditor uses the execCommand method and the built-in browser'sUnderline command to apply or remove underline formatting to / from the selected content. This browser command however works only for <u> tags, but not with inline "text-decoration: underline;" css style attributes. RadEditor uses the browser's Underline command because in other case there could arise problems with selections, nested tags and not well formed HTML content.
Kind regards,
Rumen
the Telerik team
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