•  Visual impairments > Such as blindness, low or restricted vision, or color blindness.
•  Motor skills > Such as the inability to use a keyboard or mouse, or to make fine  movements.
•  Hearing impairments > Such as reduced or total loss of hearing
•  Cognitive abilities > Such as reading difficulties, dyslexia or memory loss.

Web accessibility :                                                                                                                      Web accessibility refers to the inclusive practice of making websites usable by people of all abilities and disabilities. A complete accessible website is one which completes the following criteria:
1.If Site have textual equivalents for images and links named meaningfully,so that blind user can use text-to-speech s/w.
2.Text and images are enlarged so that  users with poor vision will access the appn.
3.Links are underlined (or differentiated) so that they will be accessible by color blind person.
4.Clickable links area is large so that user who cannot control mouse with a precision will not face any difficulty.
5.Videos are close captioned or available in sign language ,so that deaf and hard-of hearing users can access the application
6.Content is written in plain text alongwith simple diagrams and animations ,people facing dylexia and learning incapabilities better understand the content.Assistive technologies used in accessibility testing are :
1. Screens readers
2. Screen magnifiers
3. Speech recognition
4. Keyboard overlays