As mentioned in Poor Design Speaks Louder Than Words: A Lesson in Personal Branding, ineffective and unattractive design elements can send your visitors running for the browser back button. Using center-aligned body copy is another way to put readers off.
Why It’s Bad
Centered text can be difficult to read because each line starts in a different place. This can be irritating to some readers since it actually slows down the speed of reading.
Here’s an example. See how it takes more effort to read a block of text that’s center aligned?
That’s because your eyes have to keep searching for the beginning of the next line. Sometimes it’s to the left of the prior line, sometimes it’s to the right of it.
Center-aligned text is especially problematic when it’s used for long paragraphs or posts. So do your readers a favor and left-justify your text! (It’ll look nicer, too!)