If I have visited a site (URL), the link shows in a different color from links I have not visited, i. e. finds the link in a history file. How do I set how long a link is retained in history. I seem to recall, a few releases back, that there was a setting in Firefox Options for this. Now I can find a setting to delete/not delete history at logoff, but nothing to set how long an entry is retained if I don't delete at logoff.