For those of us who need to know if something is “off” by a pixel, this is a great way to do so in any application at any time.
Open the “Universal Access” Preference Pane and on the default tab “Seeing” is the “Zoom” on/off radio button. Click the “on” radio button and then configure the amount of zoom in the “Options” button to the right.
Test it by pressing Option-Command-+(plus) and you’ll zoom in in no time. To get out of the zoom, press Option-Command–(minus).