I just changed my blog so only my friends should be able to read the posts. My visitor log shows unknown visitors though. What is going on - has someone hacked my blog?and there we see a question from someone who doesn't know about search engine cache.
If you make your blog private, the search engines won't index your newer posts, but what's already indexed will stay in cache. And if someone sees a search page entry, and clicks on it, they'll get (among other things) "View Cached Content", and they'll read the cached posts.
The search engines won't care that you made the blog private. This will be similar to a deleted blog - you can delete, or make the blog private, and what's in cache will stay in cache. And you'll keep getting readers, to the cached posts.
When you make your blog private, the "robots.txt" file is updated. Here's a copy of the file for this blog, "blogging.nitecruzr.net", which is public (you are here - D'ohh).
And in comparison, here's the file for "private1.nitecruzr.net", which is private. If you don't have access to this blog, you won't see anything.
There are two differences here.
- The sitemap for "blogging.notecruzr.net".
Sitemap: http://blogging.nitecruzr.net/sitemap.xmlwhich isn't present in "private1.nitecruzr.net", since private blogs have no feeds, and no sitemaps.
- Search engine spiders are forbidden access to private blogs.
And there's a third issue here. New readers will use the search engines (and possibly "View cached content"), but your established readers will have the blog bookmarked and cached on their computers. Until the cache expires on their computers, they'll see your blog, too. And, they will continue to trigger the visitor meters.
So, if you make your blog private, after it's been well known for a while, don't expect your visitor meters to go immediately to zero. And be aware that a private blog may still be visible to uninvited guests.