As someone who works with the web I typically want my photoshop measurements in Pixels (px) opposed to inches, picas, or any of the other measurements they offer.
To change this to pixels:
- File >> Preferences
- Go to "Units & Rulers"
- Change the Units to "pixels"
Also, if you want to be able to resize things in pixels be sure to have the "Resample Image" box checked. That will result in the top pixel section being editable.
