The cause is that the mishmashes you use have to dole out a twofold purpose: They should communicate a basic theme to your web site and, more prominently, make it easy for your visitors to perceive and read.
The very high contrast between white and black, having conflicting locations on the chromatic scale, is excellent for standard paper books but not for the Web! A good selection of colors as a tool in the distribution of information is something that should be given serious consideration.
The printed media's classical plan of black lettering over a white background doesn't work well for Web content. Certain colors produced by the glowing phosphor of PC monitors are very strong and not soothing to eyes with their potency, such as when you look at snow in bright sunshine.
The above cause is why many folks will print an eBook to learn it: They can't take the "white assault" from most monitors.
Application programmers and savvy website designers are discovering this destructive quality of monitors and are compensating by making the backgrounds of their web sites an off white/gray.
You can attempt this for yourself: read a page with an complete white background and then the same page with a very light gray or pastel background. Find the difference?
The common look and color combination of your web site should be pleasing and related to the interests of your users however; the areas devoted to text should not strain their eyes. As a case, I was at a hardware forum and somebody had written a couple of bright fluorescent orange text on a medium gray background it was about all I could take! Just looking at the 2 lines of text to read them was painful.
Another case of a bad selection for body copy is a dark font over a dark background because it overtaxes the eyes to make out the text. The same cause absolute white is harmful applies to white lettering over a black background.
White without a small amount of compensating color is very traumatic on the eyes. If you ever spend any time at a site that causes such irritation, you'll drop focus and get tired on account of the strain of reading.
All the basics of your web site decoration should conspire to make the visit a pleasant one for your users. Designing and building a victorious web site should take into consideration all the design elements to keep from physically irritating your users.
