There are many examples of good practices in regards to the accessibility features on this website:

1. Website is accessible without the use of a mouse; can use up/down arrows to scroll, tab to access the menus and subpages. This supports users with a motor impairment as the interface is operable by different means of interaction.

2. The website provides an accessibility tab for viewers who require assistive technologies, including a form with clear instructions. It also uses alt text to describe images, which is important for visually impaired users who require on screen readers to access web content. The alt text can be viewed by clicking on the HTML of the image, falling under the Robust principle, as it can be interpreted by assistive technologies

3. There is a high colour contrast between the text on the website and the background, making it easier for viewers with visual impairments to navigate. Complies with the Perceivable principle as the information is easy to see and understand.

4. Clear headings which can help screen reader users understand page structure and more easily navigate through sections. Aligns with the Understandable principle with its simple layout and information.

A bad practice of accessibility:

1. A lot of the NIH subpages contain long blocks of dense text, technical language, and minimal visual chunking which can be overwhelming for users with cognitive or learning disabilities. This affects the Understandable principle as it may limit comprehension.