A text equivalent for every non-text element shall be provided (e.g., via "alt", "longdesc", or in element content).
Every image on your web site must have alternative text including alt="" for images that do not carry important information or that are redundant. Audio content must have captions and/or transcripts. Use the longdesc attribute and/or in-line text to describe images like charts or graphs where the alt-text does not carry equivalent information.
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