AFAIK,
The origins of this is advice I attribute to Joseph Holmes (as in
www.josephholmes.com). That's where I first heard it:
You view your image in PS with a neutral grey/gray background to help ascertain colour/color casts (even ones you weren't aware of before...), and viewing it on the
white bg gives you a more accurate idea of the true
contrast of your image. (ie. viewing your pic on a
black bg on a monitor will
always make it look more fabulous and contrasty than it really is, and as a result your printed image will look washed out).
All assuming viewing a file on a calibrated monitor, etc.
And an Elektra Micro-Casa Leva coffee machine. As reliable as two sticks, they don't break down, and make unreal coffee. If you take the time to learn how to handle it... just like colour management and listening to Joseph Holmes. I wonder, how many colour-management fanatics are also coffee and coffee-machine fanatics...
For what it's worth,
Kaisa Breeden