If you’re seeing 404 error pages on your websites with 1and1 hosting today, then it may be down to the fact that 1and1 have forced migration to a newer database system. For the technical, this means that they switched off MySQL 4 and forced use of the newer and more secure MySQL 5.
The result? Well those sites that depend on a database (such as those powered by WordPress, Drupal etc) will not work unless upgraded.
My advice would be to get a better host, I have seen lots of reports of poor support from 1and 1 for hosting at all levels. My personal preference is Servint who offer great support, good prices and rock-solid uptimes. Full review of Servint here