Screen zoom is a useful feature of Mac OS X that zooms into the screen where ever the cursor is located. The feature was enabled by default in prior versions of Mac OS X whenever the control key was held down, but in OS X 10.7 Lion it has been turned off by default and is now a feature of Universal Access.

How to Enable Screen Zoom in OS X Lion

• Open System Preferences from the Apple menu 
• Click on “Universal Access” and then click on the “Seeing” tab
• Check the box under “Zoom” to “ON”

Now with Screen Zoom turned on, the feature can be accessed with either the trackpad, mouse, or keyboard:

Zoom with Trackpad or Mouse
For trackpads, scrolling is achieved with two fingers gesturing up or down, with a mouse it’s simply the scrollwheel in either direction, with both you need to hold down the Control key to access.

• Control+Scroll Up to zoom in
• Control+Scroll Down to zoom out

Zoom with Keyboard
New to Screen Zoom in OS X Lion are keyboard shortcuts to zoom in and out:

• Command+Option+= to zoom in
• Command+Option+- to zoom out