In my previous post, I stated that I had some unpublished work that I needed to take care of. Over half a year ago, I laboriously hand-coded my "Neural Net Mathematics" course midterm and final in the MathML language so that I could eventually publish them on my website for future reference. This was a major effort so I was quite concerned recently when I thought I had lost the files. I was able to find copies in a personal online archive and publish them today as part of the CroftSoft Tutorials.
If it were not for the online copies, I am not sure I could have recovered these files. I used to download my personal e-mail but now I leave it in an online archive maintained by a third-party service independent of my Internet Service Provider (ISP). More and more these days I am finding that any files on my hard disk are eventually lost when the drive crashes or I switch computers. Any paper copies tend to get buried and forgotten in the folders and stacks. Those notes that I publish online on my website, however, are preserved and accessible forever.