code: function setDocType($iframe, doctype){
                  var win, doc;
                  win = $iframe.get(0);
                  win = win.contentWindow || win.contentDocument || win;
                  doc = win.document || win.contentDocument || win;
                  doc.open();
                  doc.write(doctype);
                  doc.close();
              }
docs: Add doctype to fix the style difference between printing and render