When an image contains words that are important to understanding the content, the alt text should include those words. This will allow the alt text to play the same function on the page as the image. Note that it does not necessarily describe the visual characteristics of the image itself but must convey the same meaning as the image.
An image on a Website provides a link to a free newsletter. The image contains the text "Free newsletter. Get free recipes, news, and more. Learn more." The alt text matches the text in the image. <img src="newsletter.gif" alt="Free newsletter. Get free recipes, news, and more. Learn more.">
An image on a Web site depicts the floor plan of a building. The image is an image map with each room an interactive map area. The alt text is "The building's floor plan. Select a room for more information about the purpose or content of the room." The instruction to "select a room" indicates that the image is interactive.
Glasp is a social web highlighter that people can highlight and organize quotes and thoughts from the web, and access other like-minded people’s learning.