That could if you reset the pref that makes Firefox create these default bookmarks or otherwise do not keep its value.

• browser.bookmarks.restore_default_bookmarks = false

When this pref is true then a new set of default bookmarks will be created.

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

Thank you for the prompt reply. browser.bookmarks.restore_default_bookmarks was set to false. I noticed this problem happening about a month or so ago. A dozen computers I worked on last year which are virtually identical did not have this problem. I deleted those bookmarks and they remained deleted. Those machines run version 46. Does the about:config setting have a corresponding file that I could copy from one of the working computers?

It is best not to copy the entire prefs.js file because the file contains a lot of data about the state of the browser, but compare the two files to see if you can isolate pref(s) that are about this problem.

I did copy the pref.js file over (before I read your warning) and that did fix the problem. These are simple catalog computers, so not much different between each one (and we would hope they are are the same anyway). Thank you very much for your time and help.