In Eclipse I am getting 5 warnings for my build.xml:
taskdef class.org.apache.catalina.ant.InstallTask cannot be found taskdef class.org.apache.catalina.ant.
Guess you might have to do this change, since there is no more details in your question
I beleive you might have the above settings in your build.xml Please, change ${appserver.home} to the directory that contains the tomcat installation