<! DOCTYPE html> <html lang="en">
<head>
    <meta charset="UTF-8"> <title>Title</title> <! -- Mobile device preferred --> <meta name="viewport" content="width=device-width, initial-scale=1"> <! --> <link rel="stylesheet" href="bootstrap/css/bootstrap.css"> <! -- Bootstrap. js must be imported in jquery. js before importing bootstrap.js --> <script type="text/javascript" src="bootstrap/js/jquery.min.js"></script>
    <script type="text/javascript" src="bootstrap/js/bootstrap.js"></script>
    <style>
        div[class^="col-md"]{
            border: solid 1px red;
        }
        .row{
            margin-bottom: 20px;
        }
    </style>
</head>
<body>
    <div class="container"> <! This is made up of rows and columns --> <divclass="row">
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div> </div> <! -- column offset --> <divclass="row">
            <div class="col-md-2 col-md-offset-2">col-md-2</div>
            <div class="col-md-3">col-md-3</div>
            <div class="col-md-4">col-md-4</div>
        </div>
    </div>
</body>
</html>
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Nested columns

To nest content again using the built-in raster system, you can add a new.row element and a series of.col-sm-* elements to existing.col-sm-* elements. A nested row can contain no more than 12 columns (there is no requirement that you fill all 12 columns).

<! DOCTYPE html> <html lang="en">
<head>
    <meta charset="UTF-8"> <title>Title</title> <! -- Mobile device preferred --> <meta name="viewport" content="width=device-width, initial-scale=1"> <! --> <link rel="stylesheet" href="bootstrap/css/bootstrap.css"> <! -- Bootstrap. js must be imported in jquery. js before importing bootstrap.js --> <script type="text/javascript" src="bootstrap/js/jquery.min.js"></script>
    <script type="text/javascript" src="bootstrap/js/bootstrap.js"></script>
    <style>
        div[class^="col-md"]{
            border: solid 1px red;
        }
        div[class^="col-sm"]{
            border: solid 1px red;
        }
        .row{
            margin-bottom: 20px;
        }
    </style>
</head>
<body>
    <div class="container"> <! This is made up of rows and columns --> <divclass="row">
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div>
            <div class="col-md-1">col-md-1</div> </div> <! -- column offset --> <divclass="row">
            <div class="col-md-2 col-md-offset-2">col-md-2</div>
            <div class="col-md-3">col-md-3</div>
            <div class="col-md-4">col-md-4</div> </div> <! Nested columns --> <divclass="row"> <! --div.col-md-2.col-md-offset-2-->
            <div class="col-md-2 col-md-offset-2">col-md-2</div>
            <div class="col-md-3">col-md-3</div>
            <div class="col-md-4">col-md-4
                <div class="row">
                    <div class="col-sm-4"> column nested </div> <divclass="col-sm-4"> column nested </div> <divclass="col-sm-4"> column nested </div> <divclass="col-sm-4"> column nested < / div > < / div > < / div > < / div > < / div > < / body > < / HTML >Copy the code