code: public static boolean isHtmlFileExtension(String extension) {
  		for (final String ext : HTML_FILE_EXTENSIONS) {
  			if (Strings.equal(ext, extension)) {
  				return true;
  			}
  		}
  		return false;
  	}
docs: Replies if the given extension is for HTML file.
  
  @param extension the extension to test.
  @return {@code true} if the extension is for a HTML file.