Input is Always HIGH

Development Tools IDE 1.x
1

I bought my Arduino 2 days ago .
I connected my Arduino TMP36 but it isn't stable and when I removed it analog reads something bigger than zero.

Now , I'm trying my change with digitalRead but this isn't work neither.

int ledPin = 13;


void setup()
{
  Serial.begin(9600);
  pinMode(ledPin,OUTPUT);
  pinMode(8,OUTPUT);
  pinMode(10,INPUT);
}

void loop()
{
  digitalWrite(10,LOW);
  digitalWrite(8,HIGH);
  if(digitalRead(10) == HIGH)
  {
    Serial.println("hey!");
  }
}

When ever something touch (even nothing connected cable) 10th pin it writes "hey!" I just confused.

Sorry about my english.

--

Things going even stranger when something approach 8-9-10 th pins its alert :astonished:

2

Without a pull up, the pin is floating.
You turn off the pull up every time through loop().