CSS switching for legacy browser (also CSS3 polyfill)

// JS

var isIE = /*@cc_on!@*/false;
if (isIE)
{
    ////////////// specify CSS for IE ______________________________________
    var appVersion = window.navigator.appVersion.toLowerCase();
    var isIE6 = appVersion.indexOf("msie 6.0") > -1; 
    var isIE7 = appVersion.indexOf("msie 7.0") > -1; 
    var isIE8 = appVersion.indexOf("msie 8.0") > -1; 
    var isIE9 = appVersion.indexOf("msie 9.0") > -1; 
    if(isIE6) $('html').addClass('ie6')
    else if(isIE7) $('html').addClass('ie7')
    else if(isIE8) $('html').addClass('ie8')
    else if(isIE9) $('html').addClass('ie9');
    
    ////////////// CSS3 polyfill by CSS PIE _______________________________
    $.getScript('./js/PIE.js', function(){
        if (window.PIE) {
            $('selector').each(function() {
                PIE.attach(this);
            });
        }
    });
}

// CSS
.class {
something: 0;
}
.ie6 .class {
something: 1;
}
.ie7 .class {
something: 2;
}