Dynamically change favicon from CSS. (does not work on Internet Explorer and Safari)

change-favicon-from-CSS.js

/*! dynamically change favicon from CSS (does not work on Internet Explorer and Safari)
 *
 * use with:
 * <link id='linkCSS' href='my.css' type='text/css' rel='stylesheet' />
 * <link id='favicon' rel="shortcut icon" href="../images/favicon.png" type="image/png" />
 *
 * my.css can contain:
 * #favicon { background-image: url(any valid URL); }
 */

(function () {
    var rules = document.getElementById('linkCSS').sheet.cssRules;
    for (var i = 0; i < rules.length; ++i) {
        if (rules[i].selectorText != '#favicon')
            continue;
        var m = /url[(]['"]?([^'")]+)['"]?[)]/.exec(rules[i].cssText);
        if (m) {
            var old = document.getElementById('favicon'),
                link = document.createElement('link');
            link.id = old.id;
            link.rel = old.rel;
            link.href = m[1];
            old.parentNode.replaceChild(link, old);
            return;
        }
    }
})();