Can you provide just a few more details? Front brakes? Rear brakes? Do you mean the tires skid? What if you don't push so hard on the brake pedal? Do they release as soon as you release the pedal or will the brakes stay applied for a while? What have you checked so far? Examine the rubber bladder seal under the master cylinder reservoir cap to see if it's ballooned up and mushy. Does the parking brake work properly and release completely?