html doctype adds whitespace?

Question

can someone please explain to me why having a doctype of

and

Answer 1

As you can see in this table, the first Doctype triggers quirks mode in all browsers, the second will trigger standards mode.

The rest of this story is continued at Images, Tables, and Mysterious Gaps:

Setting images to be blocks

The first choice, and one that will work for most graphically-intense designs, is to convert the image from being an inline element to a block-level element. Do that, and it no longer generates a line box, and so the problem goes away-- assuming that the image is the only thing that occupies that table cell. In the simplest case, we might add a style like this:

td img {display: block;}