body,
html {
    width: 100%;
    height: 100%;
    font-size: 62.5%;
    /*这样会使1rem=10px;或者子元素的1em=10px*/
}

html,
body,
div,
span,
object,
iframe,
h1,
h2,
h3,
h4,
h5,
h6,
p,
blockquote,
pre,
abbr,
address,
cite,
code,
del,
dfn,
em,
img,
ins,
kbd,
q,
samp,
small,
strong,
sub,
sup,
var,
b,
i,
a,
dl,
dt,
dd,
ol,
ul,
li,
fieldset,
form,
label,
legend,
table,
caption,
tbody,
tfoot,
thead,
tr,
th,
td,
article,
aside,
canvas,
details,
figcaption,
figure,
footer,
header,
hgroup,
menu,
nav,
section,
summary,
time,
mark,
audio,
video {
    margin: 0;
    padding: 0;
    border: 0;
    outline: 0;
    box-sizing: border-box;
    position: relative;
}

input,
button,
textarea,
select {
    outline: 0;
    box-sizing: border-box;
}

h1,
h2,
h3,
h4,
h5,
h6,
em,
i {
    font-weight: 100;
    font-style: normal;
}

ul,
ol,
li {
    list-style-type: none;
}

a {
    text-decoration: none;
}

button:active {
    transform: translateY(2px);
}