Highly recommended fonts for legibility:
Verdana
Georgia
Lucida Grande (Mac)/Lucida Sans (Win)
Florida Tech recommends using Lato as the primary font for body text on the web.
Best Practices:
Use simple, familiar, and easily parsed fonts.
Avoid character complexity and ambiguity.
Consider spacing and weight.
Ensure sufficient contrast between the text and the background.
Avoid small font sizes and other anti-patterns.
Avoid excessive italics and bold.
Avoid using underlines.
Avoid using strike-through, superscript, and subscript.
WCAG doesn’t establish a minimum text size, though an informal standard of 12 (=16px) for the body is generally recommended and no smaller than 9 pt (=12px).
Source: WebAIM Typefaces and Fonts
Accessible Titles and Text- recorded training session on creating accessible titles in box titles, rich text areas.