Sketch errors

Hi, I have a arduino eleven and im still fairly new to it. I have a shield on top of it and 4 servos connected in parallel on a breadboard with rails to the arduino. 3 of the servos are connected positive,negative and signal together on the breadboard and the 1 servo has only the the signal connected to the breadboard and the 5v wire and GND to the shield.
I uploaded this sketch for the servos to work and it did work

 #include <Servo.h>

 // Set digital pin numbers:
 const int servoPin = 9;  // The number of the Servo pin
 const int buttonPin = 8;  // The number of the Pushbutton pin

 int buttonState = 0;  // Variable for reading the pushbutton status
 int directionState = 0;  // Variable for reading direction of the servo

 Servo myservo;  // Create servo object to control a servo

 int pos = 0;  // Variable to store the servo position


 void setup() {
   myservo.attach(9);  // attaches the servo on pin 8 to the servo object
   pinMode(buttonPin, INPUT);  // initialize the pushbutton pin as an input
 }

 void loop(){
   // read the state of the pushbutton value:
   buttonState = digitalRead(buttonPin);

   if (directionState == 0){
     //The button is pushed
     if (buttonState == HIGH) {
       directionState = 1;// The direction for the servo is clockwise

       // goes from 0 degrees to 180 degrees in steps of 1 degree
       for(pos= 0; pos <=90; pos =pos+90)
       {
        myservo.write(pos);  // tell servo to go to position in variable ‘pos’
         delay(15);  // waits 15ms for the servo to reach the position
       }
     }

  } else if (directionState == 1) {
     // The button is pushed
     if (buttonState == HIGH) {
       directionState = 0;  // The direction for the servo is anti-clockwise

       // goes from 180 degrees to 0 degrees in steps of 1 degree
       for(pos= 0; pos <=90; pos =pos+90)
       {
         myservo.write(pos);  // tell servo to go to position in variable ‘pos’
         delay(15);  // waits 15ms for the servo to reach the position
       }
     }
   }
 }

and then i decided to upload this new sketch to my board and i had left it for a while
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#include <Servo.h>

Servo myservo; // creating myservo object
int buttonPin = 8;
int servoPin = 9;
int buttonState = 0; // set buttonState 

void setup()
{
myservo.attach(servoPin); 
pinMode(buttonPin, INPUT); 
}


void loop()
{ buttonState = digitalRead(buttonPin); // read and save to the variable "buttonState" the actual state of button
if (buttonState == HIGH)
myservo.write(0); else
myservo.write(90);

}

but now when i try to upload the first sketch, it would upload but the servos keep jerking to their position. Any ideas?

Powering servos from Arduino is not a good idea. They can need a lot more power supply current than Arduino can supply. 5V regulator is only good for 800mA and will likely go into thermal shutdown before reaching that. Use a separate supply; connect its ground to the servo grounds and to the arduino ground.