Even as a neophyte I like to solve my problems myself. Now I am clueless. The white screen of death appeared (No visible site, http://www.mozaik-coaching.be, no access via admin). A very recent thread talked about it, but I can't find it back.
probably the problem is caused by a new plugin (I cannot remember the name). WORDPRESS support suggests to access to the site via FTP. However, i do not know how to do that.