code: public static HtmlTree IFRAME(String src, String name, String title) {
          HtmlTree htmltree = new HtmlTree(HtmlTag.IFRAME);
          htmltree.addAttr(HtmlAttr.SRC, nullCheck(src));
          htmltree.addAttr(HtmlAttr.NAME, nullCheck(name));
          htmltree.addAttr(HtmlAttr.TITLE, nullCheck(title));
          return htmltree;
      }
docs: Generates a IFRAME tag.
  
  @param src the url of the document to be shown in the frame
  @param name specifies the name of the frame
  @param title the title for the frame
  @return an HtmlTree object for the IFRAME tag