So why are designers resorting to lighter and lighter text? When I asked designers why gray type has become so popular, many pointed me to the Typography Handbook, a reference guide to web design. The handbook warns against too much contrast. It recommends developers build using a very dark gray (#333) instead of pitch black (#000).
The theory espoused by designers is that black text on a white background can strain the eyes. Opting for a softer shade of black text, instead, makes a page more comfortable to read. Adam Schwartz, author of “The Magic of CSS,” reiterates the argument:
The sharp contrast of black on white can create visual artifacts or increase eye strain. (The opposite is also true. This is fairly subjective, but still worth noting.)
Let me call out the shibboleth here: Schwartz himself admits the conclusion is subjective.