yeah id say its down to abs/the rear brakes.when your cornering then the weight is going onto that side,like ant said the rear brakes warning light is the HB light.Get your rear brakes checked.Could be shoes/pads bit hard to figure out as you havnt put what car you have.
If its not the brake fluid level. This could also be caused by a ABS Sensor cable on the front check the cables that run next to the brake hoses if there is wear on the cable and the slightest bit of wire showing when it touches metal the handbrake light will illuminate indicating a fault with ebd (electronic brake distribution) i had this issue on my 1.8 when cornering and found the N/S front abs sensor cable had worn to show the inner wire, bit of insulation tape sorted it....
My light keeps coming on as well,but it's the handbrake that's too free! It lifts up off the switch going over bumps. I'll have a look at it this weekend and see if it'll tighten up a bit.