RESOLU - Reset.css ou * {margin:0; padding:0;}

<style type="text/css">
@import url(reset.css);
@import url(style.css);
</style>

#container div, #container span, #container applet, #container object, #container iframe, #container h1, #container h2, #container h3, #container h4, #container h5, #container h6, #container p, #container blockquote, #container pre, #container a, #container abbr, #container acronym, #container address, #container big, #container cite, #container code, #container del, #container dfn, #container em, #container font, #container img, #container ins, #container kbd, #container q, #container s, #container samp, #container small, #container strike, #container strong, #container sub, #container sup, #container tt, #container var,
#container b, #container u, #container i, #container center,
#container dl, #container dt, #container dd, #container ol, #container ul, #container li, #container fieldset, #container form, #container label, #container legend, #container table, #container caption, #container tbody, #container tfoot, #container thead, #container tr, #container th, #container td {
	margin: 0;
	padding: 0;
	border: 0;
	outline: 0;
	vertical-align: baseline;
	background: transparent;
}

#container #header #menu {clear:both; margin-top:30px;}

britanicus75 a écrit :
Dans mon exemple le margin-top:30px n'apparait pas pareil entre IE et Firefox. Dans firefox il remet mon div à margin:0 qui vient du reset.css.

britanicus75 a écrit :
Pour remettre les valeurs par défaut du type h1, p et autre sans espacement.

/* Page */
html {
	font-size: 100%;
}
body {
	margin: 0;
	padding: 1em;
	/*
	font-family: Arial, Helvetica, "Liberation Sans", FreeSans, sans-serif;
	font-family: Verdana, "DejaVu Sans", "Bitstream Vera Sans", Geneva, sans-serif;
	font-family: Georgia, "DejaVu Serif", Norasi, serif;
	*/
	font-size: .85em;
	line-height: 1.1;
	color: black;
	background: white;
}

/* Titles */
h1, h2, h3, h4, h5, h6 {
	margin: 1em 0 .5em 0;
	font-weight: bold;
	font-style: normal;
}
h1 {font-size: 1.75em;}
h2 {font-size: 1.5em;}
h3 {font-size: 1.25em;}
h4 {font-size: 1em;}
h5 {font-size: 1em; font-weight: normal; font-style: italic;}

/* Lists */
ul, ol {
	margin: .75em 0 .75em 32px;
	padding: 0;
}
li {
	margin: 0;
	padding: 0;
}
dl {
	margin: .75em 0;
	padding: 0;
}
dt {
	margin: .75em 0 0 0;
	padding: 0;
	font-weight: bold;
}
dd {
	margin: .25em 0 .25em 32px;
	padding: 0;
}

/* Paragraphs */
p {
	margin: .75em 0;
}
li p, blockquote p {
	margin: .5em 0;
}
address {
	font-style: normal;
}

/* Quotations */
blockquote {
	margin: .75em 0 .75em 20px;
	padding: 0 0 0 10px;
	border-left: solid 2px #ccc;
}
q {font-style: italic;}
cite {font-style: italic;}
/* blockquote, q {quotes: none;} */

/* Links */
a {
	color: mediumblue;
	text-decoration: underline;
}
a:visited {color: indigo;}
a:hover, a:focus, a:active {color: crimson;}
a img {border: none;}

/* Misc inline elements */
em {font-style: italic;}
strong {font-weight: bold;}
del {text-decoration: line-through;}

/* Forms */
form, fieldset {
	margin: 0;
	padding: 0;
	border: none;
}
input, button, select {
	vertical-align: middle;
}

Florent V. a écrit :
Non, j'utilise en général une feuille de styles qui unifie les quelques différences marquées entre les navigateurs, et qui ressemble à ça: