padding and margin BOTH add to the div's width and height

i never knew that when we specify

style="width: 600px; padding: 100px; margin: 80px; border-width: 60px"

all the padding, margin, and border ADD TO the 600px...
so the whole area essentially becomes 600px + (100 + 80 + 60) x 2 =
1080px

at first I thought the padding goes inside the width of 600px and
makes the area inside for display only 400px.

an example is at

http://www.0011.com/test_size3.html