Did you know that approximately 15% of the Canadian population (over 4 million people) have reported some type of disability? Consequently, web content authors have the potential to negatively impact thousands and possibly millions of people in Canada alone. This is not intentional. It is often done unknowingly by the inappropriate use of web page design elements and attributes. In many cases, no one is more surprised than the technically astute content authors, who are unaware of how assistive devices, such as screen readers, work or how the use of text size and color can eliminate readability entirely.
This article focuses on web page images and web accessibility. Images, such as photos, illustrations, icons, logos, etc., are not viewable by millions of web browser users. Although images represent a useful approach to enhancing web pages as well as to improving accessibility, it is also important to convey the image information in an alternate form, outside of the image. Following this practice will ensure that people who cannot view an image still have access to the image information. The Alt ("alt=") attribute of the image tag ("img=") exists for this specific purpose.
The Alt attribute is an essential element of web accessibility. When used appropriately, an "alt=" specification allows web page visitors who depend upon screen readers to obtain the necessary information they need about the content of web page images. A screen reader is a software application that enables people with severe visual impairments to use a computer. With regard to web pages and images, the screen reader uses a speech synthesizer to read back the text enclosed inside the Alt attribute. If the Alt attribute is blank or ambiguous, so is the image, and thus what a sighted person sees is not what a blind person hears.
The following are recommendations for the appropriate use of the Alt attribute when using images on web pages to make the information in them accessible to all viewers:
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