I have a 2000 ford taurus and i have no reverse lights.I changed the bulbs and checked the fuse.The brake lights and tail lights work.my high mount brake light does not work.

Check BackUp Module, generally is located in the rear quarter panel (drivers side).

If you are saying a tail light does not work, and you have changed the bulb, have you checked for voltage and ground at the socket ?
Could be a faulty socket or wiring problem.

does the high mounted brake light work? the brake switch has 2 contacts one for the high mount (LT BLUE/BLACK) and one for the tail brake lights. The tail/brake light wire is LIGHT BLUE. the main connector between the brake light switch and the tail lights is C208 which is located behind the rear seat, left side. So if there is power coming out of the brake switch OK and no power at the tail lights, check that connector. Hope this helps.

its likely the turn signal switch (multi function switch) if the hi-mount still works,

wiring issue need to trace the wiring to the light

bulbs are good the the headlamp switch is bad. the brake light switch is good if those light up

ckeck all your bulbs on your vehicle ..one of them could be out causing others not to work ...check your fuses first ...for your tail lights ....good luck ..if you need more help let me know

You have a bad connector or wire. Use a multimeter to check the wire and connectors from both lights. My bet is on the wire.

tail lights work on a different filament than the rest of the lights you mentioned, it is possible both bulbs are burned out for that filament. if not, check the fuses as the tail light circuit in some cars is on a seperate fuse. the remaining possibility could be bad socket contacts.

clean bulbs socket out using the electronic spray cleaner for electrical connectors.