Well, if it appears in any of the lists I put up every few days in Usenet comp.software.year-2000 then I have visited that link within the last 48 hours.
I create Slug's Little Lists using SPAD (as I happen upon new links I jot them down). From time to time I go online and paste the URL into Netscape. So the lists themselves are used to access the Web, thus ensuring that the URL is at least correctly spelled.
If I find a non-existent link (Error 404 etc) it gets trashed on the spot.
I usually Bookmark the pages and as I run "Whats New" on the Bookmarks every so often I see which pages have changed. I try them again and if they work they get pasted into the current little list.
That is why duplicates appear in the Lists from time to time.
But I am having difficulty keeping up. Y2K weblinks are exploding at the moment.
The little lists are then converted and loaded into a database called WEBREF which gets updated from time to time and made available via FTP.