function powerGallery() {
    $("#previous_screenshot").click(function(){
        $(".screenshots img.selected").each(function(){
            if ($(this).prev(".screenshot").length) {
                $(this).removeClass('selected').prev(".screenshot").addClass('selected');
                }
            });
        return false;
        
    });
    $("#next_screenshot").click(function(){
        $(".screenshots img.selected").each(function(){
            if ($(this).next(".screenshot").length) {
                $(this).removeClass('selected').next(".screenshot").addClass('selected');
                }
            });
        return false;
    });
}
jQuery(function($) {
    powerGallery();
});