现场演示：我的 HTML 文档

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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>CSS Opacity Using RGBA Colors</title>
<style>
    body {
        background-image: url("/examples/images/pattern.jpg");
    }
    p{
        padding: 20px;
        background: rgba(0, 0, 0, 0.6);
        color: #fff;
        font: 18px Arial, sans-serif;
    }
</style>
</head>
<body>
    <p>Setting background transparency without affecting the text content.</p>
</body>
</html>