Put “alt” or equivalent attributes to followings elements:

• Images
• Logos
• Embedded multimedia (audio and video)
• Buttons
• Icons
• Charts
• Tables
• Iframes
• Catpcha

Images

• Use “alt” attribute if a short description is sufficient.
• In a case where an image conveys complex meaning such as graphs, charts, or diagrams, provide long text description nearby in addition to the short description in the alt tag.
• Avoid redundant links to a same destination. An example would be to provide image link while having a text linked to the same destination.

If the images are purely decorative and doesn’t convey any meanings or links, you can just give null alt text (alt=””) to that image.

Forms

• Form buttons: should have a descriptive value.
• Form inputs: should have associated text labels.

Iframes

iframes should be appropriately titled.

Buttons

Buttons should have descriptive value.

Embedded Multimedia (Audio and Video)

Embedded multimedia including audios and videos should be provided with descriptive text, caption, or text version of narration available online

Captcha

When a captcha is used to confirm that the content is accessed by a person rather than a computer, text alternative forms of captcha should be provided.

Logos

Use descriptive text such as “logo of xyz organization” instead of just “logo” or “xyz organization”