Apart from the ui being neat and simple, Is there any other reason why every major website uses a white background with very few colors?
closed as not a real question by JonW♦ Apr 17 '13 at 16:26
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There are two main factors that influence the fact that most websites use a light background, the first is the power of defaults and the second is readability.
Defaults and standards
The second reason is that dark text on light backgrounds is better for readability, and this is a very controversial topic.
Text readability depends on a bunch of factors: mainly contrast, but also font size, color and lighting conditions.
Contrast and color choices
Assuming that the contrast is right and equivalent (W3C Accessibility Guidelines on contrast) for both light-on-dark and dark-on-light, it seems that for readability purposes the best thing is dark text over light backgrounds:
Here is also another source that collected some studies on the topic:
And here is another study on the topic: Letter identification performance is better for negative contrast than positive contrast.
However, some people prefer the opposite (although I didn't find any evidence), ie. light text over dark background when they're reading in dark rooms, in fact, most ebook readers have the two options:
To let the content stand out, you want a neutral background to build on. If you use to much colors and color patterns, the background seems more important than the content and structure.
Reference: About.com > White
Reference: The Color White
Simply put I think its just harder and costs more to design a site in dark colours than white colours.
Firstly as pointed out in other answers contrast is king when it comes to readability and black on white is easier to read rather than white on black, but not that much easier. I read books on my Android phone with white text on a black background and have no issues reading it.
So some niche sites that want to stand out will use a dark background but all major sites are compelled to use a white background.