This brings up a much more serious issue: valuable sites that do go away.
Right now I have saved links to over 300 photo websites and occasionally I'll encounter a dead link with no way to get to the pages which were once there. I'm not sure if the internet archive site ("wayback machine") will have it.
I think the only safe recourse is to save local copies of the web pages or to print the site contents on paper.
I copy important web pages and discussion threads to my own computer, using the "save as" command and giving each page a new name that starts with a date code. Not every browser performs this operation the same way, of course, but I use Safari and have had no problems.