What happens if my computer or browser crashes mid-edit, or if the server does not respond?

In case of a crash you'll lose your edit. To some extent, you can guard against this by editing in a text editor, for major work (but note that with regard to a system crash this does not help, unless you save frequently to disk). When you get a time-out when you try to save, you might or might not lose your edit depending on your web browser. Some browsers (e.g. Opera and Mozilla Firefox) will recover the text you have tried to save if you use the back-button. In other browsers you will lose your edit. You can protect against this by copying the text (at least to the clipboard of your system). If you did not do this, you can at least recover the latest reviewed version by using the back-button and refreshing the page.