Basics

Key Objective: Readability

Less is more when it comes to readability on a computer screen (electronic media) Sans (Ariel or Verdana) Sans-serifs look more modern and open. Sans-serif fonts are more readable than Serif on computer monitors or flat screens, because they are cleaner.
Verdana was developed specifically for electronic media. The most readable sans-serif fonts are broad, allowing ample space between letters, ample square space for each letter and more recognition. Ariel is less square and equates well for limited areas where you need lots of content. Ariel is Sans-serifs so it maintains a more modern and open look while using less space as Verdana.

Emphasis
Create emphasis but use it them sparingly. Draw attention to a whole line, by using a coloring fonts, capitalizing one word or Bolding, which increases readability more than underlines or italics.

Italics have a softer emphasis than bolding but they can have a same effect as fussy fonts at small resolutions, reducing readability. Verdana and Ariel that work well on screen can have poor readability
in italic form.

Contrast on pages
It's very important to have sufficient contrast between content, images and background. Limited or less contrast especially in the text to background is less readable slightly more tiring (consider your viewers).

Capitalization
ALL CAPS DECREASE THE CONTRAST BETWEEN LETTERS AND AS A RESULT ALSO DECREASE RECOGNITION. (just NOT a good idea)