html - 位置:固定； CSS 不工作

Question

当我将位置固定应用于我的标题时。正文内容与标题重叠!为什么会这样？而且，我该如何解决这个问题？它发生在 Firefox 和 Chrome 中。我添加了代码，只有 css 有什么问题？

html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed, 
figure, figcaption, footer, header, hgroup, 
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
    margin: 0;
    padding: 0;
    border: 0;
    font-size: 100%;
    font: inherit;
    vertical-align: baseline;
}
article, aside, details, figcaption, figure, 
footer, header, hgroup, menu, nav, section {
    display: block;
}
body {
    line-height: 1;
    width: 1351px;
}
ol, ul {
    list-style: none;
}
blockquote, q {
    quotes: none;
}
blockquote:before, blockquote:after,
q:before, q:after {
    content: '';
    content: none;
}
table {
    border-collapse: collapse;
    border-spacing: 0;
}
body {
    color: #A2A2A2;
    padding-top: 0px;
    font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif;
    position:relative;
    z-index:-1;
}
a {
    color: #0090D8;
    text-decoration: none;
}
a:hover,
a:focus {
    text-decoration: underline;
}
#container {
    width: 100%;
    margin: auto;
    padding: 0px;
    background-color:#EBEBEB;
    position:fixed;
}
header {
    font-family: 'Open Sans', 'Helvetica Neue', helvetica, arial, sans-serif;
    font-weight: 300;
}
header:after {
    content: '';
    display: block;
    clear: both;
}
header #logo {
    float: left;
    color: #0090D8;
    padding-top: 17px;  
    font-size: 30px;
    font-style: 700;
    padding-left: 15px;
}
header nav {
    margin-top: 3em;
    float: right;
}
header nav ul {
    margin: 0;
    padding-bottom:0px;
    float: right;
}
header nav li {
    display: inline;
}
header nav li + li {
    padding-left: 4px;
}

Answer 1

将您的 HTML 正文位置设置为“相对”并应用 Z-Index -1。