2. getElementById - Calculator
Enter the first and the second value and choose an math operation. Press "Calculate"
4. Traverse DOM (IE version) - absolute
Find the first, the forth tag and the first child of the forth tag name insight the body, a parent of the button which is clicked without using its name/id
5. Traverse DOM - relative
try to add rows and notice that the change button should modify content of a cell in
the same row. It is achieved by finding the first cell relatively ("in the same row") using parents