Technique C9:Using CSS to include decorative images

Applicability

Any technology that can use CSS to include images.

This technique relates to 1.1.1: Non-text Content (Sufficient).

Description

The objective of this technique is to provide a mechanism to add purely decorative images and images used for visual formatting to Web content without requiring additional markup within the content. This makes it possible for assistive technologies to ignore the non-text content. Some user agents can ignore or turn off CSS at the user's request, so that background images included with CSS simply "disappear" and do not interfere with display settings such as enlarged fonts or high contrast settings.

Background images can be included with the following CSS properties:

  • background,
  • background-image,
  • content, combined with the ::before and ::after pseudo-elements,
  • list-style-image.

This technique is not appropriate for any image that conveys information or provides functionality, or for any image primarily intended to create a specific sensory experience.

Examples

Example 1: Background image for an HTML page

The stylesheet for a Web page specifies a background image for the whole page.

…
  <style type="text/css">
    body { background: #ffe url('/images/home-bg.jpg') repeat; }
  </style>
</head>
<body>
...

Example 2: Background image with CSS for image rollovers

The stylesheet for a Web page uses the CSS background property to create a decorative rollover effects when a user hovers the mouse pointer over a link. 

a:hover { background: #ffe url('/images/hover.gif') repeat; color: #000;
  text-decoration: none;
}

Example 3: Background images with CSS to create rounded corners on tabs or other elements

The styleseet for a Web page uses the CSS background property to create rounded corners on elements. 

…
  <style type="text/css">
    div#theComments { width:600px; }
    div.aComment { background: url('images/middle.gif') repeat-y left top; 
    margin:0 0 30px 0; }
    div.aComment blockquote { background: url('images/top.gif') no-repeat left top; 
    margin:0; padding:8px 16px; }
    div.aComment div.submitter { background:#fff url('images/bottom.gif') no-repeat left top; 
    margin:0; padding-top:30px; }
  </style>
</head>
<body>
  <div id="theComments">
    <div class="aComment">
      <blockquote>
        <p>Hi John, I really like this technique and I'm gonna use it on my own Website!</p>
      </blockquote>
      <div class="submitter">
        <cite><a href="http://example.com/">anonymous coward</a> from Elbonia</cite>
      </div>
    </div>
    <div class="aComment">
…
 </div>
</div>
…

Other sources

No endorsement implied.

Tests

Procedure

  1. Check for the presence of decorative images
  2. Check that they are included with CSS

Expected Results

  • If #1 is true, then #2 is true.