I usually use grids to design website layout, it’s really useful. I found a plugin for Photoshop that will help creating grids more easily and powerful.
With GuideGuide, it doesn’t have to be. Pixel accurate columns, rows, midpoints, and baselines can be created based on your document or marquee with the click of a button.
As the image show below, the tool is easy to use, you just generate the width and height of grid as you want and all done. GuideGuide has its basic rows, columns and midpoints, but with a little creativity it can do a whole lot more.
Frequently used guide sets can be saved for repeat use. Grids can use multiple types of measurements. Best of all it’s free.
Link: GuideGuide