It was so simple. All you wanted was a local copy of your browser history so you could read offline. So you hacked up a script and it worked pretty well. But there were gaps. Sometimes pages didn't work by the time you tried to download them. Sometimes the server errored out. Once, the jerk next door dug up a cable line and your net connection went down entirely.
Errors are going to happen, so how do you handle them in code?