This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
These are warning messages only and are nothing to worry about. Struts is just telling you that it found your browser set to the locale en_US and that there is no corresponding properties file with that suffix, so it's reverting to the default, which is ActionResources.properties. If you want these messages to go away, just copy ActionResources.properties to ActionResources_en_US.properties.