How to Use Before and After Pseudo Elements in CSS
Pseudo-elements are one of the more advanced selectors that are available for use in CSS. The main purpose
behind these selectors is to create unique styling, without altering the HTML document that is used to create
the basic structure of a given webpage.
Cascading Style Sheets (CSS)
Cascading Style Sheets, or CSS, is a style sheet language used for describing the presentation of a document written in
a markup language such as HTML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.
CSS is designed to enable the separation of presentation and content, including layout, colors, and fonts. This separation
can improve content accessibility, provide more flexibility and control in the specification of presentation characteristics,
enable multiple web pages to share formatting by specifying the relevant CSS in a separate .css file which reduces
complexity and repetition in the structural content as well as enabling the .css file to be cached to improve the page
load speed between the pages that share the file and its formatting.
Separation of formatting and content also makes it feasible to present the same markup page in different styles for
different rendering methods, such as on-screen, in print, by voice (via speech-based browser or screen reader), and
on Braille-based tactile devices. CSS also has rules for alternate formatting if the content is accessed on a mobile
device.
The name cascading comes from the specified priority scheme to determine which style rule applies if more than one rule
matches a particular element. This cascading priority scheme is predictable.
The CSS specifications are maintained by the World Wide Web Consortium (W3C). Internet media type (MIME type) text/css
is registered for use with CSS by RFC 2318 (March 1998). The W3C operates a free CSS validation service for CSS
documents.
In addition to HTML, other markup languages support the use of CSS including XHTML, plain XML, SVG, and XUL.
Source: Wikipedia
CSS Articles
CSS: Cascading Style Sheets
Cascading Style Sheets (CSS) is a stylesheet language used to describe the presentation of a document written
in HTML or XML (including XML dialects such as SVG, MathML or XHTML). CSS describes how elements should be
rendered on screen, on paper, in speech, or on other media.
The 30 CSS Selectors You Must Memorize
So you learned the base id, class, and descendant selectors—and then called it a day? If so, you're missing
out on an enormous level of flexibility. You owe it to yourself to commit these advanced CSS and CSS3 selectors
to memory.