how to add a background image to entire page in html code example

Example 1: css background image full screen responsive

html { 
  background: url(images/bg.jpg) no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}

Example 2: html background image fit to screen

body {
  background-position: center;
  background-repeat: no-repeat;
  background-size: contain;
}