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Alignment

There’s a definite hierarchy here that shows where the designers want you to start first, and where they want you to go from there. They make very effective use not only of the left-to-right and top-to-bottom principles, but also of size variation to show that you need to start with the big picture at the top-left, then turn to the long banners at the right, and then read the smaller squares below from left to right. And visually, keeping everything within a tight, well-aligned grid makes the whole thing very aesthetic, easy to look at, and easy to navigate.
Source: http://www.lds.org/