The kind of taste I'm referring to is defined by Webster's as "critical judgment, discernment, or appreciation." In the same way, Webster's defines style as "a particular form or design of something."
When we think about graphic design or website design, we obviously bring to the table our own sense of taste and style. The same is true of our clients, and (presumably) we have been selected due to an aesthetic we possess that makes sense to and/or has a pleasing effect on our clients.
In other cases, clients come to us so that they don't have to think about the design elements for their project. They know they need it to look good, and they know they can trust us to implement a design that will be cool, as well as functional.
Keeping a handle on aesthetic attributes is a fluid pursuit. By that, I mean that styles change, and public tastes evolve. Staying ahead of the game requires flexibility, as well as a sense of timing.
None of this is set in stone, either, due to the subjective nature of it all. You can put two equally qualified designers in a room and get different answers to some seemingly fundamental questions.
So when it comes to defining taste and style in words, we´ll leave it to Webster's. Otherwise, in the infamous words of United States Supreme Court Justice Potter Stewart, "I know it when I see it."