Nothing. If you can't post anything/ aren't able to post anything then don't post anything. Wait until you can post something then do the following.
- Let your readers know that you couldn't post anything because (insert your reason here*) by sharing a post with them.
- Post what you were going to post before (insert reason here*).
One way you could post something/let your subscribers know that you could post something is by going to a library and posting/letting your subscribers know that you couldn't post.
*If your reason is because your dead, then this wouldn't work.I wouldn't know what to do if that was the case.