我想在html页面中用js做一个网页的公共部分，应该怎么写函数，怎么引用啊？

var html="你的html代码"

document.write(html)

HTML文件

<script type="text/javascript" src="JS文件"></script>

body,div,dl,dd,dt,ul,li,h1,h2,h3,h4,h5,h6,input,form,a,p,textarea{

margin:0px

padding:0px

}

ol,ul,li{

list-style:none

}

a{

text-decoration: none

display: block

color:#fff

}

img{

border:none

display: block

}

.clearfloat{

zoom:1

}

.clearfloat:after{

display: block

clear:both

content:""

visibility:hidden

height:0

}

还是这个

.public-container{

/*position:relative如果子元素没有绝对定位的，其实是不需要写这个的*/

position:relative

width:1100px

margin:0 auto

}

.public-header .header-logo{

float:left

background-image: url("../images/logo.png")

margin-top:40px

}

.public-header .header-logo a{

width:182px

height:54px

}

.public-header .header-nav{

float:right

margin-top:44px

}

.public-header .header-nav .item{

float:left

margin-left:50px

/*color: #3b3b3b这里写是没用的*/

}

.public-header .header-nav a {

color: #3b3b3b

}

.public-header .header-nav a:hover{

text-decoration: underline

}

.public-footer{

height:218px

background-color: #3b3b3b

padding-top:100px

}

.public-footer .footer-col{

width:230px

float:left

margin-right:60px

font-size:16px

color:#fff

lineheight:1.8

}

.public-footer .footer-col:last-child{

margin-right:0px

}

.public-footer .footer-logo{

width:182px

height:54px

margin-top:-10px

margin-bottom:10px

background-image: url("../images/logo-white.png")

}