When the mouse enters the image replace the class 'not-over' with 'over'. When the mouse leaves the image replace the class 'over' with 'not-over'. These two classes switch between a dotted border and a solid blue border.

$proto('#avatar', {
  Mouseover: {
    onMouseover: {
      ReplaceClass: {
        removeClass: 'not-over',
        addClass: 'over'
      }
    }
  },
  Mouseout: {
    onMouseout: {
      ReplaceClass: {
        removeClass: 'over',
        addClass: 'not-over'
      }
    }
  }
});

ReplaceClass with Mouseout and Mouseover