css文字水平居中

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Text Centering Example</title>
    <style>
        .centered-text {
            text-align: center;
        }
    </style>
</head>
<body>
    <div class="centered-text">
        <span>This text is centered horizontally.</span>
    </div>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Block Centering Example</title>
    <style>
        .centered-block {
            width: 200px;
            margin: 0 auto;
            background-color: #f0f0f0;
            padding: 20px;
            text-align: center;
        }
    </style>
</head>
<body>
    <div class="centered-block">
        This block is centered horizontally.
    </div>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Flexbox Centering Example</title>
    <style>
        .container {
            display: flex;
            justify-content: center;
            width: 100%;
        }
        .centered-block {
            width: 200px;
            background-color: #f0f0f0;
            padding: 20px;
            text-align: center;
        }
    </style>
</head>
<body>
    <div class="container">
        <div class="centered-block">
            This block is centered horizontally using Flexbox.
        </div>
    </div>
</body>
</html>