Remove all the HTML tags and display a plain text only inside (in case XML is not well formed)

Consider using the open source HTML Agility Pack library (htmlagilitypack.codeplex.com).

It lets you use XPATH queries to access very specific parts of an HMTL document, and the HTML does not have to be valid, well-formed XML. In addition to accessing the raw inner text of an element you can select specific attribute values, which is useful for getting things like meta description content or image alt/title text.