The alignment of text in your documents can influence whether people read down your page or scroll past what you have to say. This advice is based on the F-shaped reading pattern, the way that people skim for headings and keywords as they scroll down a text. That same idea comes into play with the tip to avoid centered text alignment in your documents.
When you center text, the left margin zig zags back and forth down the page, which makes it hard to read in the F-shaped pattern that people prefer.
Instead of skimming down the left margin to look for the highlights and headings, the eye has to search back and forth for the information on the page, as shown in the image on the right.
Watch the Lynda.com tutorial video, Favor flush-left, ragged-right body text (4m14s), for additional explanations and tips on this important guideline for the way that text is aligned on a page. The video is free with your VT login. Follow these instructions to login.