<div id="abc">
    <div class="class1">
        <div>
            1
        </div>
    </div>
    <div class="class2">
        <div>
            2
        </div>
    </div>
    <div class="class3">
        <div>
            3
        </div>
    </div>
</div>​​​​​​​​

var a = document.getElementById('abc'),
    b = a.getElementByClassName('class2');

b[0].parentNode.removeChild(b[0]);