Jetty is case sensitive on some operating systems, and not on others. This is painful when collaborating on a project with Windows users for example, where parts of the interface break because tapestry encourages case insensitivity, and windows developers see no harm in following suit.
Resources referenced with the wrong case simply don't load.
Tomcat 6.7 addresses this issue by unifying case-sensitivity accross all platforms, to address security issues (i.e. wEb-iNf) and to make applications portable.
I would like to see jetty do this too, being a cross-platform server, it seems to make no sense to have such large platform-dependent differences.