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Add alt text and title if you want your images to be conveyed to all users.
If the picture is purely decorative, provide at least null alt text (alt=””).
Avoid text in images. If it is impossible, make sure that this text is repeated in alt text.
Other Considerations:
Accepted banner images include JPG, JPEG, and PNG files.
Very large images are not recommended; at best they can be disorienting and at worse they can be an impediment.
Images that are much wider horizontally than they are tall tend to work best for course site banners.
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