//当屏幕宽度小于480px的时候，引入demo.css
<link type="text/css" rel="stylesheet" href="style/demo.css" media="only screen and (max-480px)"/>
//当屏幕大于685px的时候，启用的css样式,(内联写法)
@media screen and (min-width : 685px){
.header-top,.search-left,.search-right,.header-nav,.header-nav ul{
padding: 0 !important;
}
.search-right input{
200px !important;
}
}