CSS tutorial

Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language like HTML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript. The css code look like this:

body {
  background-image: url("bgImage.jpg");
  background-repeat: no-repeat;
}

.text1 {
    font-size: 20px;
}

@media (max-width: 1199px) {
    font-size: 16px;
}

article h2[id]:before {
 display: block;
  height: 50px;   /* equal to the header height */
  margin-top: -50px;  /* negative margin equal to the header height */
  visibility: hidden;
  content: "";
}

There are several popular frameworks, such as Bootstrap, which are more convenient than plain CSS.