The Ford Focus is a front-wheel drive car that uses a transverse-type transmission. This means that the transmission is positioned so that the length of the transmission is parallel to the firewall. This also means that the driveshafts are in the front of the vehicle. The driveshafts transmit the power from the transmission to the drive wheels. When these shafts fail, you must get them replaced immediately because the car simply won't move without them.
Turn the steering wheel on your Ford Focus all the way to the right or left. Due to the steering wheel lock, you may need to turn the key in the ignition to the "II" position.
Look behind the wheel. There will be a driveshaft running from the back of the wheel to the transmission. On this driveshaft, there will be two rubber boots, one at each end of the driveshaft.
Inspect the boots for rips or tears. Driveshafts fail when these boots rip (they eventually will rip or come apart from the shaft). These boots are called "CV boots" and protect the CV (Constant Velocity) joint from damage. Inside the boot is axle grease. This grease lubricates the joints. When the boot fails, the grease leaks out, and the joint dries out. This, in turn, causes the joint to grind and the driveshaft to fail. When this happens, you need to replace the shaft.