背景透明

禁用ie9滤镜
:root .concentration .left .content ul li .fc,
:root .concentration .left .content ul li .try-btn {filter:none;}

background:rgba(255, 155, 37, 0.7);
filter:progid:DXImageTransform.Microsoft.gradient(startcolorstr=#B3FF9A26,endcolorstr=#B3FF9A26);