public Slide showPreviousSlide() {
		if(slidePanel.currentSlide.getSlideID() > 0){

			nextSlideButton.setBorderPainted(true);

			if (slidePanel.currentSlide.getSlideID() ==1){

				previousSlideButton.setBorderPainted(false);

			}
			int previousSlideID = slidePanel.currentSlide.getSlideID() - 1;
			Slide previousSlide = slideList.get(previousSlideID);
			slidePanel.refreshSlide(previousSlide);
		}	
		return null;
	}