string str = a.ToString();
str = Regex.Replace(str, @"</?span[^>]*>", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"&#[^>]*;", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?marquee[^>]*>", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?object[^>]*>", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?param[^>]*>", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?embed[^>]*>","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?table[^>]*>","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @" ","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?tr[^>]*>", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?th[^>]*>","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?p[^>]*>","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?a[^>]*>","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?img[^>]*>","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?tbody[^>]*>","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?li[^>]*>","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?span[^>]*>","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?div[^>]*>","",RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?th[^>]*>", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?td[^>]*>", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"</?script[^>]*>", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"(javascript|jscript|vbscript|vbs):", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"on(mouse|exit|error|click|key)", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"<\\?xml[^>]*>", "", RegexOptions.IgnoreCase);
str = Regex.Replace(str, @"<\/?[a-z]+:[^>]*>", "", RegexOptions.Ignore
html 超链接 属性
HTML 使用超级链接与网络上的另一个文档相连。
锚标签和 Href 属性
HTML 使用 <a> （锚）标签来创建连接另一个文档的链接。
锚可以指向网络上的任何资源：一张 HTML 页面，一幅图像，一个声音或视频文件等等。
创建锚的语法：
<a href="url">Text to be displayed</a>
例如：
& ......
