code: public static void addToHeader(final String scriptname) {
      if (!CssResources.isInHeader(scriptname)) {
        final LinkElement styleLinkElement = Browser.getDocument().createLinkElement();
        styleLinkElement.setRel(CssResources.REL_TYPE);
        styleLinkElement.setType(CssResources.SCRIPT_TYPE);
        styleLinkElement.setHref(scriptname);
        Browser.getDocument().getHead().appendChild(styleLinkElement);
      }
    }
docs: add css script to header.
  
  @param scriptname style sheet file to add to header