CSS background-image with question mark can't be recognized as correct path

For example:
background-image: url(http://cdn1.xxx.cn/sites/all/themes/peixun/images/w-icons.png?v=0915);

would be converted into:
background-image: url(http://xxxx.cn/sites/all/themes/peixun/images/w-icons.png%3Fv%3D0915);