This div has a width set to 400px, with 10px of padding all round and 10px margins.  The div has a grey background to show the padding, and a blue border.

The div is itself within a container div-  this has width=444px (400 width +10+10 padding +10+10 margins +2+2 borders). The container has margins and padding set to zero, and a white background.

The paragraphs have  margins set to 0, font-size set to medium, white background and green borders.

75px

This table is 500px wide and centred in the page using CSS, with cellspacing set to 10px.  Each cell has 10px of padding at top, left, bottom and right.

60px

75px

The left column has cells 75px width, the right column has cells fixed at 60px width.  The centre column takes up the remaining space. The table cells have red borders.

60px

75px

The font-size is set to "medium".  Paragraphs (<p>) in table cells have margins set to 0, and have green borders.

60px