When it comes to graphic design, strong alignment is an extremely important area, where on both a page or screen, all elements should be lined up. Strong or solid alignment produces bonds that are invisible between elements so that it is easy to see where the information links together.
An unprofessional or messy looking page is often the direct result of poor alignment making it more difficult to read because your eyes have to jump and wander on the page. Try not to mix alignments wherever possible. On a screen, if some elements are centered while others are left justified, gives the work a weak, unprofessional look.