About 10 years ago I had a site with original content, then I closed the site a few years later and now the content is only seen on the WayBackMachine. I have a new site that I would like to repost the timeless articles to and was wondering if it would be okay to do so as they were originally mine or if it would hurt my new site to do so? Would placing a note "originally posted to olddomainname.com" help? Thanks for your help in this matter.
I would go ahead and post them. If they're your content then it makes sense that you can keep using it. You can write that note but it ultimately doesn't matter. If you write that note then I would add that you also controlled that domain as well.
I would post them, although that does sound like a fairly unique situation. Have you thought of asking Google directly through Webmaster Tools? Also, does the Google even have the old site indexed any more?
does the other domain still exist, if it does do a 301 redirect to the new site, if the domain is dead then just re-post them.
if the content isn't indexed in Google (or yahoo, bing, like anyone cares about them), then there is no issue.
I would search Google to see if the content still exists in its cache. Just do a search (in quotations) for some sentences you used in the old site.
Search for the first sentence of each article in quotes just to see if that content is already indexed. It will be a quick way to determine of someone else copied and has been using your content over the years. You may find that no one is using your old content. Regardless, it's not going to hurt to republish it even IF others already have it on their site. There is NO such thing as a duplicate content penalty. It's just a little harder to get duplicate content to rank than it is original. So even if your version of the article is not considered the original, it can still outrank the others by building more links and/or scoring higher on other non-content-based ranking factors.