Answers for "how to add a background photo that covers the entire webpage html"

html background image fit to screen

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

bootstrap create full screen background image

.wrapper{background: url('/assets/64531/green_suburb.jpg') no-repeat   center center fixed;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;}