I want to tab on a tab and open 2 divs. Like:

<div id="tabs">
    <ul>
        <li class="tab1"><a href="#tab1">tab1</a></li>
        <li class="tab2"><a href="#tab2">tab2</a></li>
    </ul>

    <div id="tab1">this is tab1</div>
    <div id="tab2">this is tab2</div>
    <div id="tab3">this is tab3</div>
</div>

If I want to click tab1 tab, it shows both 'this is tab1' and 'this is tab3'. How can I achieve? Cheers.