Its sad to see the total lack of web typography when there are so many resources out there on the subject.
Richard Rutter said:
For too long typographic style and its accompanying attention to detail have been overlooked by website designers, particularly in body copy. In years gone by this could have been put down to the technology, but now the web has caught up. The advent of much improved browsers, text rendering and high resolution screens, combine to negate technology as an excuse.
One of the main confusions is the difference between hyphenations and dashes.
Hyphenations
Hyphenations are used to join compound words together. That is all.
En & Em Dashes
En and em dashes have their own purpose and should only be used for that purpose.
En dashes (–) should be used to indicate a range of numbers (10–20). Em dashes (—) should be used to indicate a sudden break of thought ("We are going to—what time is it?").