How to disable Tomcat home page
rename the ROOT app to another folder name (or delete it if you don't want to manage tomcat with the tomcat manager app)
Put the app you want to see at http://localhost:8080 in the ROOT folder
refer How to Change Default Homepage in Tomcat
EDIT:
link is broked so you can try following:
The easiest would be to have the Tomcat home page (TOMCAT_HOME/webapps/ROOT/index.jsp) perform a redirect to your start page.
Or, if you have just a single web app, you can move that to the ROOT web app.
Upload ROOT.war with some other content or alternatively try to remove the folder ROOT/ from webapps