How do you switch off the airbag light on a 2001 ford focus 2.0 zetec?

If it's on, then there's a problem. What you should do is get the codes checked for the airbag system and either fix it yourself or have someone do it for you. It might be something as simple as a collision sensor malfunctioning. Technically you might be able to clear the light by resetting the computer with a code reader, but that's dangerous and it'll probably come right back on shortly after anyways.