From the Facebook Design's Notes blog, Jul 1, 2009 posting
The following are our Design Principles. At Facebook, our design is...
Universal
Our mission is to make the entire world more open, and this means reaching every corner, every person. So our design needs to work for everyone, every culture, every language, every device, every stage of life. This is why we build products that work for 90% of users and cut away features that only work for just a minority, even if we step back in the short term.
Human
Users return to our site to be surrounded by friends and other people near to them. This is a central promise of our product, that the people you care about are all in one place. This is why our voice and visual style stay in the background, behind people’s voices, people’s faces, and people’s expression.
Clean
Our visual style is clean and understated, to create a blank canvas on which our users live. A minimal, well-lit space encourages participation and honest transparent communication. Clean is the not the easiest approach to visual style. To the contrary, margins and type scale, washes and color become more important as we reduce the number of styles we rely on.
Consistent
We invest our time wisely, by embracing patterns, recognizing that our usability is greatly improved when similar parts are expressed in similar ways. Our interactions speak to users with a single voice, building trust. Reduce, reuse, don’t redesign.
Useful
Our product is more utility than entertainment, meant for repeated daily use, providing value efficiently. This is why our core interactions, the ones users engage daily, are streamlined, purged of unnecessary clicks and wasted space.
Fast
We value our users time more than our own. We recognize faster experiences are more efficient and feel more effortless. As such, site performance is something our users should never notice. Our site should move as fast as we do.
Transparent
Users trust us with their identity, their photos, their thoughts and conversation. We reciprocate with the utmost honesty and transparency. We are clear and up front about what’s happening and why.