The idea by some web designers that a grid isn’t necessary goes to show how silly some people in our industry can be. Sure sometimes you can simply get by with a design by "eyeing" it, but a grid helps to keep the chaos under control with a bit of structure. Even the best effects and elements won’t carry a design if the grid isn’t there to prop it up.
via Drawar – Sometimes A Grid Can Save You. A grid creates structure to an otherwise unstructured document.