The following is a list of some of the main readability and usability issues:

Text alignment:

Aligning text to the left, ragged on the right, increases reading speed because the straight left edge helps to anchor the eye when starting a new line (Designing Web Usability : The Practice of Simplicity by Jakob Nielsen).

Line length:

There seems to be little agreement on the best length length for optimum reading speeds. The most commonly advice is that limiting line length to 9 or 10 words can increases speed and comprehension (based on the assumption The eye can only focus on about 3 inches of a page at a time).…