::before & ::after

https://codersblock.com/blog/diving-into-the-before-and-after-pseudo-elements/

Takes place inside the div

Now’s a good time to mention that the content property is required for a pseudo-element to be created, but as you see here, it’s fine to set it to ''(empty string).

//will select only the element with all those selectors

div.green.red-text {

// enter css here

}

// If it's the only li in its container

li:only-of-type {
// css here

}

// affects every element that doesn't have that class

li:not(.green) {

}