android error parsing error(invalid tokken0

I am working on an application, in which i have a following xml. but when i try to clean/build my project the following error occurs:

"error: Error parsing XML: not well-formed (invalid token)"

android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" 
>

<TextView
    android:id="@+id/tvDisplay"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Your total is 0" 
    android:textSize="45dp"
    android::layout_gravity="center"
    android:gravity="center"
    ></TextView>

<Button
      android:layout_width="250dp"
      android:layout_height="wrap_content"
      android:text="add one"
      android:textSize="20dp"
      android:layout_gravity="center"
      android:id="@+id/bAdd" >

  </Button>


  <Button
      android:layout_width="250dp"
      android:layout_height="wrap_content"
      android:text="Sub one"
      android:textSize="20dp"
      android:layout_gravity="center"
      android:id="@+id/bSub">

  </Button>