Is it normal to type what you mean, delete it, and type something else?

Normal. It's like thinking about what you're going to say to someone. Most of the time you'll keep your thoughts to yourself, but there will be times when you'll accidentally blurt out your thoughts.

The point is, be really, really careful where you point that mouse.

"Always write angry letters to your enemies. Never mail them." ~James Fallows

i do that on here sometimes.

Comment what you really want to say. No consequences ... It's all anonymous

Every single time.

Oops, sorry, I didn't mean to press Post Comment. What I meant was, Oh yes, that's completely normal, everyone does it! And don't be afraid of accidentally pushing Post Comment, because that almost never happens. :)

That was the stupidest thing I've ever read! Jeez, what a moron.

Normal. Totally normal.
I'll write something that I want to say as my facebook status, and then delete it and not post anything. It's kind of like writing a mean letter to a jerky boss but sending it to yourself or deleting it all together. You want to send it or post it, but you're screwed if you do so you don't.
Just be careful and don't press the post or send button!
Again, normal.

I usually end up not saying anything instead of saying something that I don't really mean, but it's normal.

i could never do that only way i would be able to vent is to tell them how ridiculous they are other wise my point wouldnt of been told :\

I think we all do that. I wake up mornings wondering if I really said that, and the last braincell that is still alive did actually make me rewrite it or hit delete. We do it in person, too. We almost say something and then backtrack before it's been said. It's entirely normal. Don't worry about it. In fact, keep doing it.