Event.observe(window, 'load', function() {
    $$('.publi_inc a.publi_box').each(function(publi) {
        var img  = publi.down('img');
        var span = publi.down('span');
        var h    = img.getHeight();

        span.setStyle({
            'height':   h + 'px'
        });

        publi.observe('mouseover', function() {
            img.hide();
            span.show();
        });

        publi.observe('mouseout', function() {
            span.hide();
            img.show();
        });
    });
});