css媒体查询用法

代码如下：

<style>
    @media screen and(min-width:300px){
        body{
            background-color:blue;
        }
    }
    @media screen and (min-width:400px){
        body{
            background-color: black;
        }
    }
    @media screen and (min-width:600px){
        body{
            background-color:#f00;
        }
    }
    @media screen and (min-width:900px){
        body{
            background-color: greenyellow;
        }
    }
    @media screen and(min-width:1200px){
        body{
            background-color:yellow;
        }
    }
</style>