This div has a width set to 360px, with 7px of padding all round and 6px margins. The div has a grey background to show the padding, and a 2px thick blue border.

The div is itself is within a container div-  this has width=390px (360 width +7+7 padding +6+6 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 the browser default, white background and green borders.

390px measure

65px

This table is 390px wide and centred in the page using CSS, with cellspacing set to 5px. Each cell has 5px of padding at top, left, bottom and right.

50px

65px

The left column has cells 65px width, the right column has cells fixed at 50px width. The centre column takes up the remaining space. The table cells have red borders.

In this cell is an image 215px wide.
215px measure

50px

65px

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

50px