protected String removeHttpProtocol(String html) {
		//remove http protocol from tag attributes
		if(removeHttpProtocol) {
			Matcher matcher = httpProtocolPattern.matcher(html);
			StringBuffer sb = new StringBuffer();
			while(matcher.find()) {
				//if rel!=external
				if(!relExternalPattern.matcher(matcher.group(0)).matches()) {
					matcher.appendReplacement(sb, "$1$2");
				} else {
					matcher.appendReplacement(sb, "$0");
				}
			}
			matcher.appendTail(sb);
			html = sb.toString();
		}
		return html;
	}