If you suspect that you've taken too long over a post in Internet Explorer, you can keep it safe by stashing a copy on the clipboard, using the following method:

Press Ctrl+A (select all), and then press Ctrl+C (copy), your text will be placed safely on the clipboard. Then, if you need to re-enter your text, you can press Ctrl+V (paste) in the new text box.

Unfortunately, I don't know of a way in IE to replicate Bitt's other tip for Firefox.