Here is a good top ten list. Everyone and their brother has one of these. This one is by Steven D. of smashingmagazine.
Number 1 and 2 are the em dash ( — )and ellipsis ( … ). I also found particular interest in number 5:
Not only is it ugly and lazy, a copyright symbol hacked together out of a capital C and parenthesis might not even cut the mustard in court. Use the real McCoy (©), and bill your clients extra for the legal advice.
I don’t know of too many web developers that follow all these rules. I’m sure now that CSS has made things a bit more standard we’ll be able to worry about smaller things, like small quotes.
