媒体查询

body{
background-color:black;
}
/* @media 媒体查询关键字
and 条件链接 ：且
偶然 或 /
@media screen and (max-width: 320px){
/ 屏幕宽度小于等于320 */
body{
background-color:crimson;
}
}
@media screen and (max-width: 499px) and (min-width:320px ){
body{
background-color:darkblue;
}
}
@media screen and (max-width: 700px) and (min-width:500px ){
body{
background-color:darkorange;
}
}
@media screen and (max-width: 700px) and (min-width:500px ){
body{
background-color:deeppink;
}
}