how to change content in css code example

Example 1: change text in a div css

button {
  visibility: hidden;
}
button:after {
  content:'goodbye'; 
  visibility: visible;
  display: block;
  position: absolute;
  background-color: red;
  padding: 5px;
  top: 2px;
}

Example 2: change text in a div css

<button>Hello</button>

button {
  background-color: green;
  color: black;
  padding: 5px;
}