In studies of CSS selectors, we have seen the :: selector at some point.
But I did not find specific reference on this keyword :: isolated. That is, I just saw it being applied in selectors mostly related to pseudo-elements.
Example:
T::first-letter
But I do not understand what it means, and I do not understand if there is any pattern that identifies a possibility of using it.
Can you help raise the reference about this?
This is called pseudo-elements and are available in most browsers .
CSS selectors usually refer to elements of the DOM, this pseudo selector :: refers to elements that are not differentiated in the DOM. It may be the first letter for example:
::first-letter {
color: blue;
}<p>Algum texto!</p>or the first line:
::first-line {
color: blue;
}<p>Algum texto!<br>e a continuação</p>or adding text that does not exist in the DOM:
p::before {
content: 'Nota: ';
color: red;
}<p>Algum texto!</p>::after
::before
::first-letter
::first-line
::selection
::backdrop
::placeholder
::marker
::spelling-error
::grammar-error