Work that has been uploaded on this site for feedback, and marked viewable by WW members or Group members only has not been published. Even work that has been set to 'veiwable by anyone on the internet' can be submitted if it has been taken off WW before submitting it.
If it has been on a blog, then, again, it is best to take it off before submitting it, because some Agents/Editors (specially magazine editors) may do a google search and will reject if if they find it on the internet.
However, it all depends on how internet-savvy the agents are, and not all of them have made it into the 21st Century
But, to be on the safe side, if you are going to submit it, then remove it from the internet first.
- NaomiM
<Added>Stricktly speaking, Blog posts are deemed to have been self-published.