C# - Filter HTML tags except some element

I'm replacing the tags with napapen but you could replace them with empty string to clear them out.
static string StripTagHtml(string html)
{
    string acceptable = "script|link|title";
    string stringPattern = @"</?(?(?=" + acceptable + @")notag|[a-zA-Z0-9]+)(?:\s[a-zA-Z0-9\-]+=?(?:(["",']?).*?\1?)?)*\s*/?>";
    return Regex.Replace(html, stringPattern, "napapen");
}