Ahem. It seems that my site was down today because I didn’t renew the registration. My e-mail app considered the reminders from my registrar as spam and apparently transferred them to my junk folder automatically. Only after I realized just now that the domain expired yesterday did I find the last reminder still in the junk folder.
I just renewed the domain and have to praise my registrar, gandi.net, because serendipita.org showed up again less than five minutes after I paid the fee by credit card. Great service!
And I set up my e-mail app to not consider their messages as junk from now on.