Electronic Books

Graphics
Because graphics are so prevalent, it is important to support them with alternate textbased
descriptions. Blind users benefit greatly; since images cannot be interpreted by a
screen reader or other device, the visually impaired rely on the content within an image??™s
alt attribute to either appear in place of an image or be read aloud by screen readers.
This also benefits visitors with low connection speeds, since many turn off images when
browsing. The markup is easy:

There??™s not much else to it. For more in-depth descriptions, you can apply a title or
longdesc attribute. The former is good for descriptive content, or even supporting content;
the latter is reserved for linking to a longer, detailed description, which might be
needed for a complex diagram or intricate illustration.
In table-based layouts, single-pixel GIFs are often used to space table cells correctly.
Complex layouts use these tiny graphic files dozens of times throughout a single page, and
each instance requires the developer to create an tag like this:

ACCESSIBILITY
57
3
However, screen readers don??™t know the difference between useful and useless images, so
if no alternative text is provided, they simply read the file name.


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