What are CSS pseudo-classes?

CSS pseudo-classes provide a way to style elements, based on changes to their state. For example, :hover can be used to apply additional styles to an element when the user's pointer hovers over it.
Pseudo-classes let you apply styles to elements in relation to the content of the document tree (e.g. :first-child), external factors such as the history of the navigator (e.g. :visited), the status of their content (e.g. :checked) or the position of the mouse (e.g. :hover).
Below is a list of the top 5 most commonly used pseudo-classes and their usage. This list is by no means complete. You should always refer to relevant documentation from authoritative sources, such as MDN for more information.

• :hover, :focus and :active are used to provide feedback for user interaction (e.g. changing a button's color on hover)
• :link and :visited are useful for styling links based on navigation history (e.g. changing the color of visited links)

Below is a list of the top 5 most commonly used pseudo-classes and their usage. This list is by no means complete. You should always refer to relevant documentation from authoritative sources, such as MDN for more information.

• :hover, :focus and :active are used to provide feedback for user interaction (e.g. changing a button's color on hover)
• :link and :visited are useful for styling links based on navigation history (e.g. changing the color of visited links)
• :first-child, :last-child, :nth-child() and :nth-last-child() are useful when working with collections of elements
• :not() is used to match everything except the given selector and can be useful in styling hard to select elements
• :lang() allows you to apply special styles based on the language of the document and is useful for multilingual websites

From 30-seconds-of-code: pseudo-classes