REGEX expression for HTML Tag cleaning

C# code for replacing either a specific tag, or removing a series of potentially malicious tags from an HTML string:

 
using System.Text.RegularExpressions 

// Replace BODY tag with "<div id="advert/">" (for later replacement with ad code, for example): 
strContent = Regex.Replace(strContent, @"</?(?I:BODY)(.|\N)*?>", "<div id="advert/">"); 


//Malicious script: replace any and all of script / body /embed / object / frameset / frame / iframe / meta / ling /style with "") 
strContent = Regex.Replace(strContent, @"</?(?I:SCRIPT|BODY|EMBED|OBJECT|FRAMESET|FRAME|IFRAME|META|LINK|STYLE)(.|\N)*?>", "");