viewport——must be filled in for mobile development, but ignored on PC.
//普通写法
<meta name="viewport" content="width=device-width,initial-scale=1">
//完整写法
<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no">
Must write a complete wording, otherwise there will be page display problems.