If you use dynamic textfield in Flash and the HTML enabled text fields fail to display formatted text. There isn’t anything wrong with your ActionScript, this happens because when you embed a font, Flash does not include the entire font family automatically. Only the plain font is embedded without the bold and italic variants.

If multiple styles of the font are used in the HTML formatting, then it’s necessary to add a dynamic text field to “manage” the embedding of the entire font family.

In the Character panel, apply each style used in the movie to at least one character in the text field.