code: public static String getRootRelativePath(String url) {
  
  		Matcher matcher = URL_SEPARATOR_PATTERN.matcher(url);
  		StringBuffer result = new StringBuffer();
  		boolean first = true;
  		while (matcher.find()) {
  			if (first) {
  				matcher.appendReplacement(result, "");
  				first = false;
  			} else {
  				matcher.appendReplacement(result, ROOT_REPLACE_PATTERN);
  			}
  		}
  
  		return result.toString();
  	}
docs: Returns the relative path of an url to go back to the root. For example :
  if the url path is defined as "/cssServletPath/css/myStyle.css" ->
  "../../"
  
  @param url
  the requested url
  @return the relative path of an url to go back to the root.