A guide to the golden ratio

I found a great website that explains what it is and how to use it (including the formula). Simply put, the golden ratio (symbol is the Greek letter "phi" shown) is a special number approximately equal to 1.618. It appears many times in geometry, art, architecture and other areas.  The idea behind it is that it creates a very visually pleasing composition. What do you think? Let me know in the comments!