Thanks everyone who replied to my posting.

Yes, electronic material is very difficult to deal with. In her article
'A blurring of the boundaries' Curator 38/1 March 1995, Elaine Gurian
discusses how we now communicate leaving no material trace (elephone,
Internet). Or we leave multiples or 'original' evidence (fax,
photograph, CDs etc).

I want to be able to cite scores of websites. As Barbara said, if I put
the cited material into an appendix, it would be extremely fat. Things
are further complicated by the fact that the URL could change after it's
been cited and I'm not sure how we can get around this unless, as Roger
said, it is kept in a central archive "(forever?)"

The solution given by John is the one I will be following if I can:

   Pitkow, J. And Kehoe, C. (1996). GVU's 6th WWW User Survey
[On-line]. Available:
http://www.cc.gatech.edu/gvu/user_surveys/survey-10-1996.(underlined)

But my difficulty is how can I cite, say, a home page? Who do I write
down as the author? The webmaster?  And the problem with just citing the
URL is that I can't really put them in alphabetical order since they
mainly all begin with http://www......... Perhaps I could start with
say, Guggenheim Museum, The. [date] http://www......Does anyone have any
ideas?
Thanks
Tricia