You'll need to remove all tags and unescape special chars.
PHP example:
$text = preg_replace($html, '<[^>]*>', '');
$text = html_entity_decode($text);
VB.NET example:
Dim text As String = Regex.Replace(html, "<[^>]*>", "")
text = System.Web.WebUtility.HtmlDecode(text)
Java example:
text = html.replaceAll("<[^>]*>", "");
For the html entity decoding you'll find a good answer here: Java: How to unescape HTML character entities in Java?. Otherwise you could just replace them if you know all of them (
, "
, ...).