The Principles of Gestalt:

Gestalt Principles in Design from Lynda.com

Here are the 6 Principles of Gestalt:

1. Proximity
2. Common Fate
3. Similarity Principle
4. The Closure Principle
5. The Symmetry Principle
6. The Figure Ground Principle

Lets look at these examples discussing Gestalt Principles in Web Design:

Gestalt for Web Designers