A headless chicken is a creature which appears whenever an error is encountered in eRepublik, either due to you following an incorrect link, an error, or the server maintenance. The chicken is in reference to the English idiom "Like a chicken with its head cut off" which means running around in a frenzied manner, as chickens can apparently do after beheading. Mike the Headless Chicken is a documented case of this actually happening.
In eRepublik, citizens can assume that anytime a headless chicken appears, the game developers are running around like headless chickens.
The headless chicken pops out of a nonexistent web page.