CSS MQ test #1

  <link href="red.css" rel="stylesheet"
 media="only screen and (max-width: 320px)">
  <link href="yellow.css" rel="stylesheet"
  media="only screen and (min-width: 641px)">
  <link href="green.css" rel="stylesheet"
 media="only screen and (min-width: 321px) and (max-width: 640px)">

The document's background should be

• red if the browser's width is lower than 320 pixels
• green if the browser's width is between 321 and 640 pixels
• yellow if the browser's width is greater than 641 pixels