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.
Accessibility
Accessibility — UX Knowledge Base Sketches
Knowledge
What's the Best Font Size For the web? Well, It Depends… — Imarc
Picking a font size for the web used to be really easy. 16 points and you’re done. You could feel confident that your content would be decently readable on PC or Mac, Netscape or IE. Man, have times changed.
Typography
What's the Best Font Size For the web? Well, It Depends… — Imarc
Jakob Nielsen's 10 general principles for interaction design. They are called "heuristics" because they are broad rules of thumb and not specific usability guidelines.