CSS pseudo-elements are powerful selectors that allow you to style specific parts of an element without adding extra markup to your HTML. They provide a way to insert content before or after an element, or to target the first letter or line of text.

Syntax and Usage

Pseudo-elements are denoted by double colons (::) followed by the pseudo-element name. The basic syntax is:

selector::pseudo-element {
    property: value;
}

Common pseudo-elements include:

::before
::after
::first-letter
::first-line
::selection

Examples

::before and ::after

These pseudo-elements insert content before or after an element's content:

blockquote::before {
    content: "\201C";
    font-size: 3em;
    color: #888;
}

blockquote::after {
    content: "\201D";
    font-size: 3em;
    color: #888;
}

::first-letter and ::first-line

Style the first letter or line of text in an element:

p::first-letter {
    font-size: 2em;
    font-weight: bold;
    color: #4a4a4a;
}

p::first-line {
    font-style: italic;
}

Important Considerations

Pseudo-elements can only be applied to block-level elements.
The content property is required for ::before and ::after to work.
Some pseudo-elements may not be supported in older browsers.
Use pseudo-elements judiciously to enhance design without cluttering your HTML.

Browser Support

Most modern browsers support CSS pseudo-elements. However, for maximum compatibility, consider using single colons (:) instead of double colons (::) for older browsers like Internet Explorer 8.

Related Concepts

To further enhance your CSS skills, explore these related topics:

Conclusion

CSS pseudo-elements are a powerful tool for adding style and content to your web pages without modifying the HTML structure. By mastering these selectors, you can create more dynamic and visually appealing designs while maintaining clean, semantic markup.