sanitize_stylesheets = function (html, tagPolicy) {
        /**
         * sanitize just the css in style tags in a block of html
         * called by sanitize_html, if allow_css is true
         */
        var h = $("<div/>").append(html);
        var style_tags = h.find("style");
        if (!style_tags.length) {
            // no style tags to sanitize
            return html;
        }
        style_tags.each(function(i, style) {
            style.innerHTML = sanitize_css(style.innerHTML, tagPolicy);
        });
        return h.html();
    }
sanitize CSS
like sanitize_html, but for CSS
called by sanitize_stylesheets