The :last-child selector allows you to target the last element directly inside its containing element. It is defined in the CSS Selectors Level 3 spec as a “structural pseudo-class”, meaning it is used to style content based on its relationship with parent and sibling content. Suppose we have an article and want to make the last paragraph smaller, to
Selectors
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, theelement, and by information from the protocol such as the HTTP Accept-Language request-header1 field. Acceptable language-code strings are specified in the HTML 4.0 specification. :lang(language-code)
The #id selector allows you to target an element by referencing the id HTML attribute. Similar to how class attributes are denoted in CSS with a “period” (.) before the class name, ID attributes are prefixed with an “octothorpe” (#), more commonly known as a “hash” or “pound sign”. <header id=”site-header”></header> #header { /* this
The :invalid selector allows you to select <input> elements that do not contain valid content, as determined by its type attribute. :invalid is defined in the CSS Selectors Level 3 spec as a “validity pseudo-selector”, meaning it is used to style interactive elements based on an evaluation of user input. This selector has one particular use: providing a user with feedback while they are interacting