where should you add a background image in html code example

Example 1: css background image

background-image: url("image.png");
background-position: center;
background-repeat: no-repeat;
background-size: cover;

Example 2: background image

div {
  background-color: #ffffff;
  background-image: url("img_tree.png");
  background-repeat: no-repeat;
  background-attachment: scroll|fixed|local|initial|inherit;
  background-position: right top  |  x% y%  |  xpos ypos;
  background-clip: border-box|padding-box|content-box|initial|inherit;
  background-size: auto|length|cover|contain|initial|inherit;
}
//shorthand:
div {
  background: #ffffff url("img_tree.png") no-repeat right top;
}

Example 3: how to add a background image in html

<!-- HTML -->
<div id="imageDiv"></div>

<!-- CSS -->
<style>
  #imageDiv {
	background-image: url('someimage.png');
  }
</style>