我制作了一个异步请求服务器端接口根据返回的JSON串判断显示不同图片的程序，是用异步加载实现的。
            document.write('<div id="' + S + '"></div>');
            var head = document.getElementsByTagName("head")[0] || document.documentElement;
            var script = document.createElement("script");
            script.setAttribute("type", "text/javascript");
            script.setAttribute("charset", "utf-8");
            script.setAttribute("src", G(Q, b) + "&d=" + (new Date()).getTime());
            script.onload = script.onreadystatechange = function() {
                if (!this.readyState || this.readyState == "loaded" || this.readyState == "complete") {
                    script.onload = script.onreadystatechange = null;
                    if (head && script.parentNode) {
                        head.removeChild(script);
                    }
                }
            };

            head.insertBefore(script, head.firstChild);

请问为什么在火狐下选项卡里的圆圈不停的转，显示还在加载。但页面上已经显示了要显示的内容。。在其他浏览器上都OK。。。请教了！