Runtime error checking

The question often arises, which error messages should one check for to make sure everything is working?
The following are the runtime error message patterns I am checking for using JMeter (via Assertion Response):

Portlet (gpir-browser-2) specific:

• "Error message" <-- Appears in most exception messages
• "An error has occurred!" <-- Appears in most exception messages
• "Stack Trace:" <-- Appears in most exception messages
• "Portlet Exception" <-- Appears in most exception messages
• "at java.lang.Thread.run" <--- appears in most java exception messages
• "Portlet unavailable!" <-- caused by a misconfigured portlet pom.xml file
• "Error contacting web service" <-- caused by incorrect webservice URL in portlet.xml for gpir-browser-2 portlet
• "The requested resource.*is not available" <-- caused by incorrectly configuring portlet in web.xml
  

Main gridsphere page specific:

• "GridSphere portal failed to initialize!" <-- Caused by a misconfigured pom.xml file
• "Stack Trace:" <-- Appears in most exception messages