Many Samsung devices store a flash counter that keeps track of how many times you have flashed custom firmwares to your device. On some devices, a yellow triangle or other sort of visual warning is also displayed during boot if you are running a custom firmware. TriangleAway was built to disable the triangle (if a visual warning is present) and reset the custom ROM flash counter to 0. This app requires root !

You can find out the current status of your flash counter and firmware state (custom or official) by booting into "download mode" on most devices. The usual way of getting into "download mode" is by first turning off your device, then turning it on by pressing and holding VolDown+(Home)+Power. Alternatively, the "adb reboot download" command also often works.

When you run TriangleAway, if your device and firmware are supported, it will show you the detected state of the binary (custom or official) and flash counter value, and the option to Reset flash counter. Please confirm that the information shown is correct before resetting the values.
Source and supporting documentation can be found here.