CSS pseudo selectors allow you to select and style specific states of an element. They are extremely useful for adding styling based on user interaction or other conditions. In this post, we'll take a look at some of the most commonly used pseudo-selectors in CSS.

What are Pseudo Selectors?

Pseudo-selectors let you select elements not just by name, id or class, but based on their state, position or other qualities. For example, you can use pseudo selectors to:

• Style an anchor tag link when it is being hovered over or clicked.

• Style a list item when it is the first or last item.

• Style an element when it is in focus, such as an input when it is selected.

Some Common Pseudo Selectors

Here are some of the most useful pseudo selectors you should know:

#:hover - Applies styles when you hover over an element with your mouse pointer. Commonly used for links, buttons, etc.

#:focus - Applies styles when an element is focused, such as a text input. Useful for forms.

#:first-child - Applies styles to the first element within a parent container.

#:last-child - Applies styles to the last element within a parent container.

#:nth-child - Applies styles based on the position of an element within a series of siblings.

#:visited - Applies styles to links that have already been visited.

#:active - Applies styles while an element is being activated by the user, such as a button while it is being clicked.

Real World Examples

Here are some examples of how pseudo selectors are commonly used:

/* Make links red when hovered over */
a:hover {
  color: red; 
}

/* Give a special style to the first list item */
li:first-child {
  font-weight: bold;
}

/* Style every other list item differently */  
li:nth-child(even) {
  background-color: #ddd;
}

As you can see, pseudo selectors open up all sorts of styling possibilities beyond just using classes and IDs. They allow CSS to be much more state and context aware.

Browser Support

The good news is pseudo selectors have excellent browser support. Most of the major pseudo selectors work across all modern browsers, even as far back as IE8. A few of the newer, more advanced pseudo selectors have less support, but all the major ones can be used freely.

Pseudo selectors are an extremely useful part of mastering CSS. They allow for very targeted styling based on user interaction and other states. Next time you're styling a website, consider where you can take advantage of pseudo selectors to create more dynamic and interactive styles!