How to Zoom In on any screen on iPhone 3G

Got troubles reading the text under an icon on your iPhone 3G? Using an application that will not permit you to zoom in on some details?
Don't worry about it, there's a simple solution built right into your iPhone that i have apply to. Just follow these instructions to switch on additional gestures that will allow you to zooming in on any screen.

For the first time, turn on zoom feature:

1. Go to Settings ---> General-- -> Accessibility ---> Zoom
2. Zoom ---> On

Zoom will enlarges the entire screen using three-finger gestures. The gestures now activated are:

1. Double-tap with three fingers to zoom in.
2. Drag three fingers while zoomed to move around the screen.
3. Double-tap and drag three fingers up or down to change the zoom level.

That' all.
Note: it won't work on Previous iPhone series !