第一種：link的方式：

1 <link rel="stylesheet" media="screen and (max-width:600px)" href="./css/blue.css">
2     <link rel="stylesheet" media="screen and (min-width:900px)" href="./css/red.css">
3     <link rel="stylesheet" media="screen and (min-width:1200px)" href="./css/yellow.css">

第二種：css的方式：

    <
 
style>
        @media screen and (max-width:600px) {
            body {
                background-color: blue;
            }
        }

        @media screen and (min-width:900px) {
            body {
                background-color: red;
            }
        }

        @media screen and (min-width:1200px) 
 
{
            body {
                background-color: yellow;
            }
        }
    </style>

媒體查詢的兩種方式