CSS Tutorial: How to Use Class Selectors to Style Specific Elements

📝 Usage

This template demonstrates how to select specific elements using HTML class attributes and apply styles to them. It is useful for styling elements with a specific class.

📘 Explanation

The following code applies CSS styles to elements specified by class attributes. In this example, we select a <div> tag with class="main" and change its text color to blue.

🔹 Partial Code (Class Selector)

/* Style specified by class */
.main {
  color: blue; /* Change text color to blue */
}

💻 Complete Working Code (Class Selector)

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>CSS Class Selector Demo</title>
  <style>
    /* Style specified by class */
    .main {
      color: rgb(27, 141, 33); /* Change text color to green */
    }
  </style>
</head>
<body>
  <div class="main">
    <h2>Heading ○○</h2>
    <p>This is a<span class="light">□□</span>.</p>
    <p>
      <a href="https://copicode.com/">Home</a>
      Go back
    </p>
  </div>
</body>
</html>

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🧩 Effective Use of Class Selectors

CSS class selectors are a flexible way to select elements using the .classname format. Unlike ID selectors, you can apply the same class name to multiple elements, making them highly reusable for styling purposes.

🔍 Features of Class Selectors

Class selectors have the following features:

Can be used multiple times on the same page
Multiple classes can be applied to one element (<div class="main light">)
CSS specificity is moderate (more specific than element selectors, less than ID selectors)

💡 Appropriate Use Cases

Class selectors are effective for elements such as:

・Reusable UI components (buttons, cards, etc.)
・State-indicating styles (.active, .hidden, etc.)
・Theme-based color styles (.primary, .secondary, etc.)

⚠️ Caution

When using class selectors, be mindful of the following:

1. Maintain consistent naming conventions (e.g., BEM methodology)
2. Avoid overly specific class names
3. Use appropriate namespaces to prevent style conflicts

🛠 Practical Techniques

To use class selectors more effectively:

・Create utility classes (.text-center, .mt-20, etc.)
・Combine with state classes (.btn.active)
・Combine with CSS variables for theme management

Class selectors are a fundamental concept in CSS design. When used properly, they allow you to create maintainable and scalable style sheets.