WebAIM - Web Accessibility In Mind

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Background Images, something new


From: Hull, Larry G. (GSFC-732.0)[GSFC]
Date: Oct 21, 2008 1:50PM


I ran across a thread that was concerned about possible problems with
the use of background images, those images provided on a page by CSS,
not coded in the source.

I knew that you couldn't see background images. We once examined a page
where an image appeared that you didn't see at all because it was a
background image and we also looked at another page where a background
image overlaid text. This text was invisible to graphic user yet made
the associated form understandable to you or to a user with images off.
Essentially, this hidden text provided a legend as opposed to a label.
It could in fact have been marked up as a legend for increased

I also knew background images wouldn't print. Actually, not printing
when the background is a color or a busy wallpaper image saves ink and
may improve readability of the hard copy.

What I didn't realize is background images also disappear when Windows
High Contrast mode is used.

Windows High Contrast mode is a Windows OS accessibility option designed
for people who have vision impairment. High Contrast increases
legibility for some users by heightening screen contrast with
alternative color combinations. Some of the schemes also change font
sizes for greater legibility.

Bottom line is that background images are invisible to screen readers,
people with images turned off, printers, and people using Windows High
Contrast mode.

Learn something new every day!

Larry (time to leave, back Thursday)