Occasionally, you'll also find a document that uses "Microsoft Smart-Quotes" or somesuch garbage. These are a result of people creating web pages in MS-Word and MS-Powerpoint. It's most often evident in single and double quoting. 0x93 and 0x94 are the pairs for double quotes, don't know about single-quotes off hand.
I'm a little unclear what the whole point of "Smart-Quotes" is, but they break things. In particular, they render as garbage on most non-MS browsers.
Rather than duplicate some already good information, here's a link to an explanation, and a Perl program that strips the offending characters out.
--Chris
e-mail jcwren