People have disappeared from my Friends List but I did not remove them and they did not remove me.

Friend removals are not caused by a technical error on the site, as it is not possible for a friend to be removed without confirmation from one of the users involved. The issue you are experiencing is caused by one of the following reasons:

1. This person removed you from their Friend List, either intentionally or accidentally.
2. This person has deactivated their account, causing them to disappear from all Friend Lists. If they choose to reactivate their account, they will reappear on these lists.

If a large number of friends disappeared from your account in a short period of time, it is possible that the security of your account may have been compromised. Please select a unique and complex password that is different from other passwords that you use on the Internet, and keep this information completely to yourself. You can reset your password by using the "Change Password" field on the Account page.

You should also make sure that all email addresses associated with your account are secure. Remember that anyone who can read your email may be able to also access your Facebook account. Additionally, please make sure that you log out of your Facebook account after each use and "quit" your browser when you’re done using the site. Never check the "Keep me logged in" box when logging in from a public computer or someone else’s mobile device, as this will keep you logged in even after you close your browser window.

Finally, please make sure that when you access the site, you always log in from a legitimate Facebook page with "facebook.com" in the domain part of the URL (web address). For more information about protecting your account, please visit the Facebook Security Page.