CSS attribute 'contain' not working

Question

I want to be able to display the entirety of an image within a div.

I'm having difficulty displaying an image with the background-size property set to contain - it does not display the whole image, only the centre, at the full size of the source image.

JSFiddle

Code

#header {
    background: rgba(0, 0, 0, 0.8);
    color: #ccc;
    text-align: center;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 3;
    padding: 20px 0;
}

#header .logo {
    width: calc(100%/3);
    height: 75px;
    margin: 0 auto;
    background-size: contain;
    background: url(http://startupweekend.org/wp-content/blogs.dir/1/files/2013/04/CokeLogo1.png) no-repeat center center;
}

<div id="header">
  <div class="logo"></div>
</div>

Answer 1

This is because you overwrite the first property, you must move background-size property after background, like so:

#header .logo {
    background: url(http://startupweekend.org/wp-content/blogs.dir/1/files/2013/04/CokeLogo1.png) no-repeat center center;
    background-size: contain;
}

This is because the shorthand background property will overwrite all preceding background-* properties whether they're included in the shorthand or not.

Shaggy comment

Answer 2

Styles will be applied from top to bottom, hence style background-size:contain; is overwritten by position described in background: url(http://startupweekend.org/wp-content/blogs.dir/1/files/2013/04/CokeLogo1.png) no-repeat center center;

You need to add background-size:contain; below the background:. Updated Fiddle

#header {
  background: rgba(0, 0, 0, 0.8);
  color: #ccc;
  text-align: center;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 3;
  padding: 20px 0;
}
#header .logo {
  width: calc(100%/3);
  height: 75px;
  margin: 0 auto;
  background: url(http://startupweekend.org/wp-content/blogs.dir/1/files/2013/04/CokeLogo1.png) no-repeat center center;
  background-size: contain;
}

<div id="header">
  <div class="logo"></div>
</div>