$.fn.arrows = function() {
  $(this).bind('keydown', function(event) {
        var lnk = false;
        var left, right;
        right = $('#pravasipka').attr('href');
        left = $('a#levasipka').attr('href');
        navigable = $('body').attr('class');
        if(navigable=='navigable') {
          switch(event.keyCode) {
            case 0x27: lnk = right; break;
            case 0x25: lnk = left; break;
          }
        }
        if(lnk) {
          window.location = lnk;
          return true;
        }
        return true;
  });
}