Thanks to google cache (all the sites containing the original info are unreachable as well) I found a notification in one of the Java User groups:
A planned downtime of three days. If we would do that at work we would get into serious trouble! We go through all sorts of efforts to ensure 24/7 availability and even if we have major site updates we don't let that impact our availability.
I noticed this because one of my tomcat instances did now want to start up which was caused by a failing XML- dtd validation.
Luckily this can be easily fixed by removing the dtd validation in the xml file. However I wonder how many tomcat servers world wide will have similar problems to start up until Monday! Such a long downtime of such "standard" URLs is rather unprofessional IMHO.