Designed for Use, 2nd Edition

Screen Edges Have Infinite Size

If you think about it, an interface element at the very edge of your screen is essentially infinite in size if you’re trying to hit it with a mouse. No matter how far in the direction of the screen edge you move your mouse, it will never leave the screen and always remain on the target. Thus, it makes sense to put important elements at the very edge of the screen. Hitting such elements is much easier because people can just slam the mouse toward the edge, and it will stop inside the target on its own.

Corners are especially valuable, because they have two infinite edges.

In most cases, this same effect does not apply ...