var browser_agent = navigator.userAgent.toLowerCase();

function is_browser (agent) {
    return browser_agent.indexOf(agent) >= 0;
}

function detect_browser () {
    var classes = null;

         if (is_browser('opera/'))        classes = 'opera';
    else if (is_browser('msie 6'))        classes = 'msie msie6';
    else if (is_browser('msie 7'))        classes = 'msie msie7';
    else if (is_browser('msie 8'))        classes = 'msie msie8';
    else if (is_browser('msie '))         classes = 'msie';
    else if (is_browser('gecko/'))        classes = 'gecko';
    else if (is_browser('konqueror/'))    classes = 'konqueror';
    else if (is_browser('applewebkit/'))  classes = 'applewebkit';

    if (classes)
        document.getElementsByTagName('html')[0].className = classes;
}

detect_browser();