::marker pseudo element in CSS

The ::marker pseudo-element is for styling the stylistic marker of a list element.

You can combine ::marker with the content property to change what the marker is.

:link pseudo class selector in CSS

The :link selector is a pseudo-class that targets all unvisited anchor (a) elements on a page.

When used in combination with the :hover, :link must be used first, or else not be defined at all, in order for the :hover styles to work. This is because they are equally specific, so if :link came after, those styles would override the hover styles.

The :link pseudo-class will target all anchor elements that have an href attribute, even if the href has an empty value.

:last-child pseudo class selector in CSS

The :last-child selector allows you to target the last element directly inside its containing element.

It is used to style content based on its relationship with parent and sibling content.

Using :last-child is similar to :last-of-type but with one important difference: it is less specific. :last-child will only try to match the very last child of a parent element, while last-of-type will match the last occurrence of a specified element.

:lang() pseudo class selector in CSS

The :lang() pseudo class selector in CSS matches elements based on the context of their given language attribute.

Language in HTML, is determined by a combination of the lang=”” attribute, the meta element, and by information from the protocol such as the HTTP Accept-Language request-header field.

#id selector in CSS

The #id selector allows you to target an element by referencing the id HTML attribute.

ID attribute values should be unique. HTML with two or more identical ids does not validate, and will produce unpredictable results.

If there are two of the same, CSS will still match and style both. JavaScript however, when querying for an ID, will find the first and stop.

ID selectors are extremely powerful. They have a very high specificity.

A valid #id cannot start with a number and must be at least one character long. id attributes and selectors are case-sensitive, and must exactly match across HTML, CSS and JavaScript.