2003 ford focus zetec ABS light flashes on intermittently. What is the cause?

Thanks Charlie,
72,000kms on the clock. All fluids are topped up and cvboots all good with no splits etc. There is a bit of dust on the back of the wheels not bad though and looks pretty clean. Am due for an oil change etc and will have techs check for fault, but had thought it may've been something easy that I could've dealt with at home ie fluid somewhere that i dont know about or faulty warning light sensor with an easy process to reset. (haha Thats what we all hope for!?) Thankyou so much for your time. First time female user here. It has been very helpful. Cheers :-) Thanks Charlie, 72,000kms on the clock. All fluids are topped up and cvboots all good with no splits etc. There is a bit of dust on the back of the wheels not bad though and looks pretty clean. Am due for an oil change etc and will have techs check for fault, but had thought it may've been something easy that I could've dealt with at home ie fluid somewhere that i dont know about or faulty warning light sensor with an easy process to reset. (haha Thats what we all hope for!?) Thankyou so much for your time. First time female user here. It has been very helpful. Cheers :-)

There is an intermittent problem with the system. You will need a scan tool to pull up the fault code to determine where to start looking.How many miles are on this vehicle? Check the front CV boots for tears. A torn CV boot will leak grease, which may coat the front wheel speed sensor(s). This will often cause them to not read the vehicle speed properly. Iron dust from "metal to metal" brakes will also collect on the tip of a wheel sensor (they are magnetic). Often the do it your-selfer will perform a brake job and not clean the metal off of the sensors. Failure to flush the brake fluid once every 2 years will also cause premature failure of the ABS control unit (very $$$ to replace, brake fluid is cheap)
Most likely causes are bad wheel sensors or bad wiring near the sensors. You won't know what is wrong without a code scanner.
Charlie
There is an intermittent problem with the system. You will need a scan tool to pull up the fault code to determine where to start looking.How many miles are on this vehicle? Check the front CV boots for tears. A torn CV boot will leak grease, which may coat the front wheel speed sensor(s). This will often cause them to not read the vehicle speed properly. Iron dust from "metal to metal" brakes will also collect on the tip of a wheel sensor (they are magnetic). Often the do it your-selfer will perform a brake job and not clean the metal off of the sensors. Failure to flush the brake fluid once every 2 years will also cause premature failure of the ABS control unit (very $$$ to replace, brake fluid is cheap)
Most likely causes are bad wheel sensors or bad wiring near the sensors. You won't know what is wrong without a code scanner.
Charlie