code: public Content getHeader(String header) {
          Content bodyTree = getBody(true, getWindowTitle(header));
          addTop(bodyTree);
          addNavLinks(true, bodyTree);
          Content h1Content = new StringContent(header);
          Content heading = HtmlTree.HEADING(HtmlConstants.TITLE_HEADING, true,
                  HtmlStyle.title, h1Content);
          Content div = HtmlTree.DIV(HtmlStyle.header, heading);
          bodyTree.addContent(div);
          return bodyTree;
      }
docs: Get the given header.
  
  @param header the header to write
  @return the body content tree