function fix_style() {
    if ($('rightzone') && $('rightzone').offsetHeight && $('content').offsetHeight && $('leftzone').offsetHeight) {
        var content = $('content').offsetHeight;
        var rightzone = $('rightzone').offsetHeight;
        var maxheight = (rightzone > content) ? rightzone : content;
        if ($('leftzone').offsetHeight < maxheight) {
            $('leftzone').style.height = maxheight + 'px';
        }
    }
}

addEvent(window, 'load', fix_style, false);