function rollover()
{
    var anchors = document.getElementsByTagName('a')
    for(var i=0; i<anchors.length; i++)
    {
        if(anchors[i].getElementsByTagName('img') &&
           anchors[i].className.match('over'))
        {
            anchors[i].onmouseover = function()
            {
                var image = this.getElementsByTagName('img')[0];
                if(!image.src.match('_over.jpg'))
                    image.src = image.src.replace('.jpg','_over.jpg');
            }
            
            anchors[i].onmouseout = function()
            {
                var image = this.getElementsByTagName('img')[0];
                if(image.src.match('_over.jpg'))
                    image.src = image.src.replace('_over.jpg','.jpg');
            }
        }
    }
}