::before/::after pseudo elements in CSS - A Complete guide

The CSS pseudo-elements ::before and ::after insert content before or after a selected element. They require the `content` property to be rendered, accepting strings, image URLs, or Unicode characters. Pseudo-elements act as if added to the DOM but aren't actually part of it, allowing styling of specific element parts. They appear within the parent element, making them suitable for container elements, not empty ones, unless wrapped in a container. These are useful for hover effects and cosmetic enhancements. The `attr()` function retrieves attribute values from an element to be used within the content of these pseudo-elements. When they overlap, ::after is on top by default but can be changed by using z-index. These elements are not part of the DOM tree and should not be used for important content due to accessibility concerns. They are inline by default.