2019独角兽企业重金招聘Python工程师标准>>> 
<html>
<head><style type="text/css">
@media only screen and (max-width:1200px){
#test{
font-size: 100;
}
}
@media only screen and (max-width: 800px) {
#test{
font-size: 50;
}
}
</style>
</head>
<body>
<div id="test">
<div style="height:2em;background-color:red"/>
</div>
</body>
</html>
and后面要有空格