I'm using Photoshop CS6 to make a menu system for a Bluray disc. I'm placing buttons using a 225 X 225 pixel grid. The grid starts at the top left hand corner as 0,0 but where I want to place the buttons, it is just a bit too high. Is it possible to move the 0 point of the grid, so that I can shift the whole grid lower? Alternatively, I suppose I could subdivide it in smaller units so that I can place the buttons in the correct place. Or I could use a guide, but the grid seems simplest.
Well, you can move the zero/origin point of the ruler and grid on any image by simply dragging the upper-left corner to where you want the new origin to be in the image itself. When you drag the origin into the image, it will give you a little crosshairs which you can use to find your new place (you can use guide lines to set these points, too). If you have dragged the origin out and want to reset, just double-click the upper-left corner and it will reset.
Forgot to mention: you must have rulers (command-R or View >> Rulers) turned on.