<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=0.5, maximum-
scale=2.0, user-scalable=yes" />
<style>
body{ font: 62.5%/1.4 Arial Sans-serif; ... }
.wrapper{ min-width:600px; width:98%; margin: 0 auto; }
.wrapper .content{ min-width:400px; width:70%; ... }
.wrapper .sidebar{ min-width:180px; width:28%; ... }
.wrapper h1{ font-size:2em; }
.wrapper p{ padding: 0 0 1em; }
</style>
body {
font: normal 100% Helvetica, Arial, sans-serif;
}
h1 {font-size: 1.5em; }
small {font-size: 0.875em;}
.main {
　　　　float: right;
　　　　width: 70%;
　　}
.leftBar {
　　　　float: left;
　　　　width: 25%;
　　}
<link rel="stylesheet" type="text/css"
　　　　media="screen and (max-device-width: 400px)"
　　　　href="tinyScreen.css" />
<link rel="stylesheet" type="text/css"
　　　　media="screen and (min-width: 400px) and (max-device-width: 600px)"
　　　　href="smallScreen.css" />

用bootstrap