code: public void fixFocus() {
  
          TextBox invisibleTextBox = new TextBox();
          Style style = invisibleTextBox.getElement().getStyle();
          style.setPosition(Position.FIXED);
          style.setLeft(-99999, Unit.PX);
          style.setTop(-99999, Unit.PX);
          m_basePanel.add(invisibleTextBox);
          // base panel is already attached at this point, so we can just set the focus
          invisibleTextBox.setFocus(true);
      }
docs: Bypasses a focus bug in IE which can happen if the user opens the HTML code editor from the WYSIWYG editor.<p>
  
  The next time they open the editor form from the same container page, the user may be unable to focus on any input
  fields. To prevent this, we create a dummy input field outside the visible screen region and focus it when opening
  the editor.