This is a basic introduction of grid systems I found on line which I think its quite useful.
The grid system in graphic design is a way of organizing content on a page, using any combination of margins, guides, rows and columns. It is commonly seen in newspaper and magazine layout with columns of text and images. One grid, or a collection of grids, may be used across an entire project to achieve a consistent look and feel. In a finished product, the grid is invisible, but following it helps in creating successful print and web layouts.
Types of Grids
There is really no limit to the grid layouts that can be created. Common types include equally sized two, three and four-column grids with a header across the top, as well as a full-page grid of squares. From these building blocks, the variation of column widths, borders, page size and other features of the grid will lead to unique page design. When starting a project or even just practicing, try using a grid system to help position the elements of your design on the page.
Breaking Out of the Grid
Once the grid is established, it is up to the designer when and how to break out of it. This doesn’t mean the grid system in graphic design will be completely ignored. Instead, elements may cross over from column to column, extend to the end of the page, or extend onto adjacent pages. Breaking out of the grid can lead to the most interesting page designs.