Type design may be intimidating to many, with terms such as leading, baseline, kerning, ascender, tail, and many more … The good news is, there are eight basic, universal typographical design elements: typeface, hierarchy, contrast, consistency, alignment, white space, and color. Even a basic understanding of each of these elements can revolutionize any design project.
Typography
Typography Elements Everyone Needs to Understand — Gravit Designer Blog
Colour contrast between text and background is important on web pages. It affects some people’s ability to perceive the information (in other words to be able to receive the information visually).
The goal of accessibility is to design & code digital products, services in a way that users with disabilities are able to use them. Your context or temporary condition and limitation also affect the way you use a product.