I'd like to caution against only selecting official sites - and those sites which have a lot of funding to hold them up. I'd like to see that encouraged to prosper as a mechanism against market oriented news reportage, which at the end of the day is quite confined to its own interests. William Shaw , Consulting Engineer, Electronic Systems Associates. Part of the freedom of the net is the freedom to reference the sites you wish to link to. Another thing to keep in mind is that students have limited space, and thus as their priorities change so does their web sites.
Old pages have to be removed in order to make room for new ones to be created.
Brian , as a University Laboratory Sysadmin, should be aware of the quotas usually applied to student accounts. I used to administer a lab of NeXTs when I was still in school, and one of the frequent issues was space. The question to be asked here is weighing the value of the link against it's 'stability'. Like Christine I see a fine line between credibility, stability, and usability. A global search engine should not limit, but a academic historical society should.