code: public String defaultDisplay(String tagName) {
      String ret = elemdisplay.get(tagName);
      if (ret == null) {
        Element e = DOM.createElement(tagName);
        Document.get().getBody().appendChild(e);
        ret = curCSS(e, "display", false);
        e.removeFromParent();
        if (ret == null || ret.matches("(|none)")) {
          ret = "block";
        }
        elemdisplay.put(tagName, ret);
      }
      return ret;
    }
docs: Returns the default display value for each html tag.