Have you ever been caught complaining that something ought to exist, only to find out that it does exist, exactly the way you want it, and, in fact, has existed for some time in that state? Your emotions do this weird thing where you're both delighted and embarrassed at the same time. That's what my emotions do, anyhow. Most recently that happened with my discovery that it's as easy as anything to use the em-dash on-line for things like this blog. If you already know this, you may well be rolling your eyes and thinking, "Yeah, so?". Hey, remember your first time.
The em-dash is that longish dash that gets used for pauses in mid-sentence. It's heavier than a comma, but (to me, there's some controversy about it) lighter than parentheses, semi-colons, or colons. They can be used to death — some of the nineteenth-century poets went a little silly with them — but they're also very handy and seem to be more in use of late.
The alternative is to type two or even three hyphens, like so: --. The problem with those on-line is that one hyphen can word wrap while the other one just sits there on the previous line. Instead of looking like you intended a longish pause in the word flow, it just looks like you can't type. There are various ways to get one entered using a word processor (most word processors will replace a double hyphen with an em-dash anyhow), but for HTML you have to write —. I guess what kept me from discovering it myself is that it's "m", not "em".
Now that I'm writing about it, I'm wondering why they're so difficult to get keyed in while semi-colons are right on the home row. Hmmmmm....