默认清除样式

html,
body,
ul,
ol,
li,
dd,
dt,
dl,
div,
h1,
h2,
h3,
h4,
h5,
h6,
span,
label,
input,
p,
i,
a {
    margin: 0px;
    padding: 0px;
    
}
a{
	list-style: none;
}
img{
border:0;
}

.clear:after{
	content: '';
	clear:both;
	display: block;
	width: 0;
	height: 0;
	visibility:hidden;
}