function ff3detect() {
    navigator.userAgent.toLowerCase().indexOf("firefox/3.") != -1 ? document.body.className += " ff3" : "";
    navigator.userAgent.toLowerCase().indexOf("firefox/2.") != -1 ? document.body.className += " ff2" : "";
    navigator.userAgent.toLowerCase().indexOf("opera/9.5") != -1 ? document.body.className += " op95" : "";
}

if (window.addEventListener){
    window.addEventListener("load", ff3detect, false);
}