JRE container on the classpath is not a perfect match
This "warning" in Eclipse had me baffled on exactly what it was wanting and more specifically on where this setting was that needed to be modified.
The JRE container on the classpath is not a perfect match to the 'JavaSE-1.6' execution environment.
So I thought this is perfect additional documentation is definetly needed out on the net, so here is my chance to add to it, and hopefully help someone in the future when they find this cryptic message. I had just been making the change over in my Eclipse RCP project to use Java 1.7 instead of Java 1.6, when this Warning from Eclipse started showing up in the my Proeblems View.
This turned out to be in the MANIFEST.MF file, on the Overview Tab, is a section titled Execution Environment. In it was listed the "JavaSE-1.6". I needed to remove the JavaSE-1.6 and add JavaSE-1.7, and the warning was resolved.