After installing Continuum 1.1 and Archiva 1.1.1 a number of web pages failed to load throwing exceptions such as javax.el.ELException: Function ‘:empty’ not found. As it turns out, this has to do with Tomcat version 6.0.18 and the EL library that it comes with.
As always, when on Linux, a script can fix things and [...]

This article describes how to upgrade Tomcat running under Plesk and how to disconnect the control Plesk has over the Tomcat server. This may not be the ideal configuration for you if you have many clients using JSP webapps. Your clients will no longer have the ability to use the Plesk war upload [...]

Plesk loves to overwrite all manual changes to the httpd.include file for your vhost. In fact, this is the normal behavior of Plesk, and you must place all changes in a separate file, vhost.conf (notice the warning inside of httpd.include)

# ATTENTION!
# DO NOT MODIFY THIS FILE OR ANY PART OF IT. THIS CAN RESULT [...]