Add Css Function

function addCss(url) {
    if (window.XMLHttpRequest) {
        xhr = new XMLHttpRequest();
    } else {
        xhr = new ActiveXObject("Microsoft.XMLHTTP");
    }
    xhr.open("GET", url, false);
    xhr.send();
    var lazyStyle = document.createElement('style');
    lazyStyle.innerHTML = xhr.responseText;
    document.head.appendChild(lazyStyle);
}
addCss('https://fonts.googleapis.com/css?family=Source+Sans+Pro:300,400,700&subset=latin,latin-ext');
addCss('css/bootstrap.min.css');