مشاهده و تمرین روی کد ها

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<title>W3.CSS</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3.css">
<body>

<div class="w3-container w3-green">
  <h1>W3Schools Demo</h1> 
  <p>Resize this responsive page!</p> 
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    <h2>London</h2>
    <p>London is the capital city of England.</p>
    <p>It is the most populous city in the United Kingdom,
    with a metropolitan area of over 13 million inhabitants.</p>
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    <h2>Paris</h2>
    <p>Paris is the capital of France.</p> 
    <p>The Paris area is one of the largest population centers in Europe,
    with more than 12 million inhabitants.</p>
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  <div class="w3-third">
    <h2>Tokyo</h2>
    <p>Tokyo is the capital of Japan.</p>
    <p>It is the center of the Greater Tokyo Area,
    and the most populous metropolitan area in the world.</p>
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چارچوب w3css