Double-Colon Notation (::)

[vanribeiro]

About the Pseudo-Elements

Browsers need to offer support to the CSS 1 and 2 and to accept the one-colon notation (:) when we use the pseudo-elements.

But following the CSS documentation, it's important to use double-colon notation (::) with pseudo-elements to make difference between it and pseudo-classes, which use one-colon notation (:). This improves the code readability and understanding.

For example:

Pseudo-elements:

p::first-line{
  color: red.
}

Pseudo-classes:

a:hover{
   color: blue;
}