I use my computers at home to host my Web-site, including this blog. But the IP address I have at home, is just a regular, dynamically-assigned IP address, which is owned by my ISP. This IP address can be reassigned to be at any moment.
Therefore, I have an update service which makes my changed IP address available to people who may want to access my URLs.
This morning, this update service failed to do its job correctly. And therefore, my Site was unavailable from 4h40 until 6h50.
This problem has now been corrected in an easy way.