Summary knowledge: HTML default style sheet CSS property rollup

css| style Sheet

*{margin:0;padding:0 at the beginning, you need to restore the HTML default CSS value when you need to use margins.

I've been looking for this document, and I happened to see it on W3 today. In addition to the definition of inline and block, it is important to note

Default styles for labels such as BODY|H1~H6|BLOCKQUOTE|MENU|UL|OL|DD (margin and font-size).

This thing is useful when you need to restore the default value. See below for details:

HTML, address,
Blockquote
Body, DD, Div,
DL, DT, fieldset, form,
Frame, frameset,
H1, H2, H3, H4,
H5, H6, Noframes,
OL, P, UL, center,
Dir, HR, menu, pre {display:block}
Li {Display:list-item}
Head {Display:none}
Table {display:table}
TR {Display:table-row}
thead {Display:table-header-group}
tbody {Display:table-row-group}
tfoot {Display:table-footer-group}
Col {Display:table-column}
Colgroup {Display:table-column-group}
TD, Th {Display:table-cell;}
Caption {display:table-caption}
th {font-weight:bolder; Text-align:center}
Caption {Text-align:center}
body {margin:8px; line-height:1.12}
h1 {font-size:2em; margin:. 67em 0}
h2 {font-size:1.5em; margin:. 75em 0}
h3 {font-size:1.17em; margin:. 83em 0}
H4, P,
BLOCKQUOTE, UL,
FieldSet, form,
OL, DL, dir,
Menu {MARGIN:1.12EM 0}

h5 {font-size:. 83em; Margin:1.5em 0}
h6 {font-size:. 75em; Margin:1.67em 0}
H1, H2, H3, H4,
H5, h6, B,
Strong {Font-weight:bolder}
blockquote {margin-left:40px; margin-right:40px}
I, cite, EM,
var, address {font-style:italic}
Pre, TT, code,
KBD, Samp {font-family:monospace}
Pre {White-space:pre}
button, textarea,
Input, Object,
Select {Display:inline-block;}
Big {Font-size:1.17em}
Small, Sub, sup {font-size:. 83em}
Sub {vertical-align:sub}
sup {Vertical-align:super}
Table {border-spacing:2px;}
THEAD, Tbody,
tfoot {Vertical-align:middle}
TD, Th {Vertical-align:inherit}
S, strike, Del {Text-decoration:line-through}
HR {border:1px inset}
OL, UL, dir,
menu, DD {margin-left:40px}
OL {List-style-type:decimal}
OL UL, ul OL,
UL UL, ol ol {margin-top:0; margin-bottom:0}
U, ins {text-decoration:underline}
Br:before {content: "\a"}
: Before,: after {white-space:pre-line}

Center {Text-align:center}
ABBR, acronym {font-variant:small-caps; Letter-spacing:0.1em}
: Link,: visited {text-decoration:underline}
: Focus {Outline:thin dotted invert}

/* Begin bidirectionality settings (don't change) * *
Bdo[dir= "ltr"] {direction:ltr; Unicode-bidi:bidi-override}
Bdo[dir= "RTL"] {Direction:rtl; Unicode-bidi:bidi-override}

*[dir= "ltr"] {direction:ltr; unicode-bidi:embed}
*[dir= "RTL"] {Direction:rtl; unicode-bidi:embed}

@media Print {
h1 {Page-break-before:always}
H1, H2, H3,
H4, H5, h6 {page-break-after:avoid}
UL, OL, DL {page-break-before:avoid}