I faced the same error. It seems that Netbeans can not deploy to Tomcat7
and Tomcat8 (Or at least i could not find the way how to do it). Netbeans
log files gives below error
TomcatManagerImpl connecting to: http://localhost:8080/manager/list
Similarly it tries to use manager/deploy for deploying.
Tomcat documentation states that after tomcat7 they changed the
structure and these two links are not available anymore.
When I installed Tomcat6 and configured at Netbeans, it worked and
deployed as expected.