All Images need to have Alternative text (ALT tag) included. To add a ALT tag to your image in the rich text editor, you will

1. Select the image and then click on the add image icon , in the rich text editor.
2. In the Image Properties window, find the alternative text field under Image Info tab, and then enter the alternative text for your image.

For infographics or other information-dense images, add the full text of the graphic elsewhere on the page. There is also an HTML longdesc tag if you are up to editing the source code:

<img src="w3html.gif" alt="W3Schools.com" width="100" height="132" longdesc="http://example.com/desc#item3">