prev/next buttons don't work when a tags are in li

[jcubic]

I have this html:

    <section class="gallery">
        <ul>
            <li>
                <a href="img/batik-01.jpg" class="fresco sb" title="Ikar">
                    <img src="img/batik-sm-01.jpg" alt="Batik: Ikar"/>
                </a>
                <p>Ikar</p>
            </li>
            <li>
                <a href="img/batik-02.jpg" class="fresco sb" title="Rozdroże">
                    <img src="img/batik-sm-02.jpg" alt="Batik: Rozdroże"/>
                </a>
                <p>Rozdroże</p>
            </li>
        </ul>
    </section>

and prev/next button don't work. probably because $(this).index('.sb'); is always 0