Hmmm…
This article says that in 2005, October 25 was “World Internet Day”:
typicallyspanish.com/cgi-bin/news/exec/view.cgi/1/278
This article mentions “International Internet Day” on October 20:
wired.com/news/culture/0,1284,21543,00.html
but I found this website for May 17, 2006:
diadeinternet.org
and the same content is also here:
internetday.info
I think that Internet Day does not exist yet because the date keeps changing.