I was just wondering why my car shakes when i step on the brakes or when i go over a certain speed. Also, i know one of my ABS sensors are bad on my right front tire and i was wondering if that was why it was shaking or if there was some other reason. If someone could please help me that would be great. i dont want to pay for stuff i dont know about and get overcharged or whatever...im not good in the brake department. thanks

If your car shakes when your braking like you said, It is probably a warped rotor or rotors. When the brakes wear unevenly, the surface of the rotor isnt smooth and flat like it should be, but rather kind of "rolls." So when the brake pad is applied, instead of being dragged smoothly across the rotor, it hits and misses because of the uneveness, causing the shake. I would get the rotors resurfaced (machined), and check to make sure you still have enough pad left

You might also want to check to make sure you didn't lose a balance weight from one of the wheels. I agree that when you step on the brake that the rotor may be warped but if you get shaking when going over a certain speed it may be a tire balance problem, bent wheel or it could even be a bad CV Joint but they often times give more warning than just a vibration.
Take your car to a tire shop and have the front wheels balanced, if this doesn't cure the shaking problem then you will have to dig further. If your are slightly mechanically inclined you can replace the rotors yourself and save some bucks. They usually cost between 30 and 40 dollars per rotor (estimate) or you can go with drilled and slotted for a few more dollars. Good Luck!

thank you guys alot, yeah i think ill just install the rotors myself. it shouldnt be that hard. thanks

All of the above are great suggestions. One that is often overlooked is if fix-a-flat was ever used. If it was, moisture is also injected into the tire throwing the tire off balance. Again, the best way to tell is to bring it to a tire shop. If fix-a-flat was used, tell the mechanic. This way he'll fix the problem, not just compensate fot the moisture with extra weights.