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Living Examples - Client-Side Image Maps |
(f) Client-side image maps shall be provided instead of server-side image maps except where the regions cannot be defined with an available geometric shape.
Image maps incorporate links or script activations into one graphical image, as opposed to using separate free-standing graphical image buttons. Client-side
image maps utilize the user agent (e.g. web browser) to determine which region the user has selected. If necessary, you can determine if the image map
is client-side by looking through the source code for a tag that begins with the word 'map'.
In the event the object does not properly load on the User Agent (e.g. web browser), alternate links must be provided.
Section 508 requires that an image map's alternative method be functional. Provide a link to a navigation bar or the actual links:
<OBJECT data="navbar1.gif" type="image/gif" usemap="#map1">
<MAP name="map1">
<P>Navigate the site.
[<A href="guide.html" shape="rect"
coords="0,0,118,28">Access Guide</A>]
[<A href="shortcut.html" shape="rect"
coords="118,0,184,28">Go</A>]
[<A href="search.html" shape="circle"
coords="184.200,60">Search</A>]
[<A href="top10.html" shape="poly"
coords="276,0,276,28,100,200,50,50,276,0">Top Ten</A>]
</MAP>
</OBJECT>
However, there are some circumstances where an image map might not be rendered by the User Agent. Also, some User Agents do not render content that is placed
inside <object> tags. Therefore, it is strongly recommended that alternate links and/or text be placed separately.
Link regions on a client-side image map are treated exactly like free-standing graphic images in the respect that they must contain alt attributes.
If the link region contains a text reference (e.g. the region leading to a search function page might simply say "Search"), the alt attribute should, at
the very least, match the wording on the image.
If the link region contains an image (e.g. a link to a search function page might have a picture of binoculars or a magnifying glass), the alt attribute
must match the destination or the function that is inferred by the image.
Although some alt descriptions can be expanded (e.g. the alt value for the region leading to a search function can say: "Search the entire site"), it is
highly recommended that the alt values are kept brief; not all User Agents and assistive technologies can handle lengthy alt values.
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Curator:
Responsible NASA Official:
Last Updated: March 6, 2009
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