I noticed that and wondered what it was about.
I clicked on one well know poster's ad that was not highlighted.
After I had clicked on it, and refreshed the main page for the gun section it became highlighted.
I still don't know why.
An enlightened zeal for the energy and efficiency of government will be stigmatized as the offspring of a temper fond of despotic power and hostile to the principles of liberty.
Alexander Hamilton, author of Federalist No. 1. 10/27/1787