Principles of graphical design

I watched quite a good video on the principles of graphical design, by Steven Wittens, which can be found here.  To try to somehow take credit for someone else’s work, and to help me understand thetopic I thought I’d try to summarize some of the things he said, and develop some of his ideas. Be aware that what I say here is as much me thinking aloud as it is summarizing someone else’s. This means you aren’t allowed  to form negative assumptions about Steven Wittens based upon what I say.