Took me a grand total of 2 min to find it using google


http://www.allstates-flag.com/fotw/flags/ufe-id.html

Lately I've noticed a black - medium blue - black, arranged horizontally auto tag on many vehicles in the area around Pittsburgh, Pennsylvania. Anyone know what this means?
John Evosevic, 3 July 2002

The Black-Blue-Black design is usually seen on a policeman's personal car or family members car. It stands for the "thin blue line". There is also a similar one with a red strip for firemen.
Jim Popovitch, 17 August 2002

The black-medium blue-black flag is actually a police mourning band. It is typically worn as a band across the badge when an officer is killed in the line of duty. I have seen it in use more frequently now as a bumper sticker, I believe this is probably a show of respect for the police officers killed on September 11th.
Troy Corwin, 26 September 2002

er at cafe-olive.com-->
I think (I m not sure) it is flag of Konigsberg (modern Kaliningrad).
Victor Lomantsov, 14 May 2003