div 背景透明,字体不透明

.demo{ 
　background:transparent;<!--背景透明--> 
　color:#fff;<!--字体颜色--> 
　background-color:rgba(255,255,255,0.15)<!--最后一个参数设置透明度，前面三个是RGB颜色值--> 
}

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
        <style type="text/css">
            .aa{
                width: 400px;
                height: 200px;
                background-image: url(../../img/360/5yuq4ivk.bmp);
                background-size: 100% 100%;
            }
            .demo{ 
                width: 200px;
                height: 100px;    
                color: yellow;                    
                /*background:transparent;*/            
                background-color:rgba(144, 238 ,144, 0.6);    
            } 
        </style>
    </head>
    <body>
        <div class="aa">
            <div class="demo">
                大家辛苦了！
            </div>
        </div>
        
    </body>
</html>