Snobs look down at you: They seem to think they're better or smarter; maybe their parents are loaded or maybe they know a lot about something. But the term actually originated as a putdown for social climbers, people aspiring to look down at somebody else.
"Snob" is believed to be an abbreviation for sine nobelitate, Latin for "no aristocratic title." In early 19th century England, a new "middle" class entered the social scene--and began sending kids to college. The universities, up till then aristocrats only, weren't too keen on accommodating the new-rich and so, according to legend, set them apart by inscribing "s.nob" next to their names.
Meanwhile, an English writer named William Makepeace Thackeray used "snob" so often in an 1840 series of articles satirizing the English obsession with social status that he is officially credited with originating the word. Whatever the source, the term quickly reached general usage to describe anyone who had succeeded in climbing the social ladder--usually by copying the manners of the upper classes and seeking out their company.
At some point in the 20th century, snobbishness became a characteristic of the upper classes themselves. And the word gradually became associated with the superior life that money can sometimes buy. Nowadays, calling oneself a snob can simply mean that you recognize "quality"--and are proud of it. Film snobs are disclosing that they know more about the movies than most people, while html snobs don't see why everyone hasn't learned the programming language by now.