Apache Tomcat is an open source Java implementation. It appears that you didn't update Java through the official Sun Microsystems (Oracle) Java site.
Afraid this isn't really correct. Apache tomcat is an open source lightweight servlet container used for hosting Java servlets - it's not an implementation of a JRE or the JDK (even if you did download it and install it by accident which is highly unlikely you'd have had to navigate to the default http://localhost:8080
for it to show up - it certainly wouldn't have just appeared at a random site.) Loosely speaking, you'd develop a Java servlet, package it up as a jar file then deploy it to your servlet container (tomcat for example) which would then display your web application.
From what you've written there it's most likely that the issue was with the site itself, and the fact you just ran a Java update was a complete coincidence. If the site was using Tomcat server side for some reason and it was misconfigured, a servlet got undeployed or someone changed the port to 80 by mistake you may well have seen that page. Either way, it was most likely a problem with them, not you.