<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
* { box-sizing: border-box;
}
.left { background-color: #2196F3; padding: 20px; float: left; width: 20%; /* The width is 20%, by default */
}
.main { background-color: #f1f1f1; padding: 20px; float: left; width: 60%; /* The width is 60%, by default */
}
.right { background-color: #04AA6D; padding: 20px; float: left; width: 20%; /* The width is 20%, by default */
}
/* Use a media query to add a break point at 800px: */
@media screen and (max-width: 800px) { .left, .main, .right { width: 100%; /* The width is 100%, when the viewport is 800px or smaller */ }
}
</style>
</head>
<body>
<h2>Media Queries</h2>
<p>Resize the browser window.</p>
<p>Make sure you reach the breakpoint at 800px when resizing this frame.</p>
<div class="left"> <p>Left Menu</p>
</div>
<div class="main"> <p>Main Content</p>
</div>
<div class="right"> <p>Right Content</p>
</div>
</body>
</html>