Difference of CSS in different document types

<! Doctype HTML public "-// W3C // dtd xhtml 1.0 transitional // en"
Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd>
· All units must be explicitly specified, such as body {margin: 0px ;}
· When specifying the width and height, you need to subtract the padding from the actual width and height. For example, the display height of a div is 200, and its padding is 10px 0px 5px 0px, the DIV height cannot be set to 200px, but should be: 185px;

<! Doctype HTML public "-// W3C // dtd html 4.0 transitional // en">
· All units are PX by default. Therefore, if it is not specified, it is equivalent to PX.
· When the width and height are specified, it is not affected by the padding.