There has been some debate in the poetry circles about whether a poem on a website is 'published'. In legal terms, as always, things aren't quite that simple.

I am no lawyer, but there is a definition of 'published work' here. The key phrases have to be 'A work is "published" when it is first made available to the public on an unrestricted basis. It is thus possible to display a work, or distribute it with restrictions on disclosure of its contents, without actually "publishing" it.' (My emphasis). (Reproduced from Nolo).

And here is another one.

Of course, different legislations create different laws.

Another term that is used loosely is 'broadcast'. Material on the web is not 'broadcast': it is not thrown out to a wide audience outside of their control. The audience chooses to take it at a time of their choosing. This is referred to as 'narrowcasting'. Awful word, but if there is a word 'broadcast' there must be an antonym.