(function($){
  
  $.fn.hoverbox = function(){
    
    var thumb_width = 125;
    var thumb_height = 125;
    var border = 1+4;
    
    $('a', this).hover(
      function(){
        var p = $('.preview', this);
        var p_width = p.width();
        var p_height = p.height();
        p.css({top: ((p_height-thumb_height)/-2)-border+'px', left: ((p_width-thumb_width)/-2)-border+'px'});
        $(this).addClass('hover');
      },
      function(){
        $(this).removeClass('hover');
      }
    );
    
    return this;
  };
  
})(jQuery);