*{padding:0margin:0}
div,dl,dt,dd,form,h1,h2,h3,h4,h5,h6,img,ol,ul,li,table,th,td,p,span,a{border:0}
img,input{border:nonevertical-align:middle}
body{font-family:Tahoma,Arial,Helvetica,"宋体"font-size:12pxtext-align:centerbackground:#FFFcolor:#000}
html{overflow-y:scroll}
ul,ol{list-style-type:none}
th,td,input{font-size:12px}
h3{font-size:14px}
button{border:nonecursor:pointerfont-size:12pxbackground-color:transparent}
select{border-width:1px_zoom:1border-style:solidpadding-top:2pxfont-size:12px}
.clear{clear:bothfont-size:1pxheight:0visibility:hiddenline-height:0}
.clearfix:after{content:""display:blockclear:both}
.clearfix{zoom:1}
a:link,a:visited{text-decoration:nonecolor:#333}
a:hover,a:active{text-decoration:underlinecolor:#f60}
其实就是对css样式进行一个初始化设置，避免CSS样式在不同的浏览器中有着不同的解释和呈现。就是在css文件的开头
下面是雅虎的 css reset
body,div,dl,dt,dd,ul,ol,li,h1,h2,h3,h4,h5,h6,pre,
form,fieldset,input,textarea,p,blockquote,th,td {
padding: 0
margin: 0
}
table {
border-collapse: collapse
border-spacing: 0
}
fieldset,img {
border: 0
}
address,caption,cite,code,dfn,em,strong,th,var {
font-weight: normal
font-style: normal
}
ol,ul {
list-style: none
}
caption,th {
text-align: left
}
h1,h2,h3,h4,h5,h6 {
font-weight: normal
font-size: 100%
}
q:before,q:after {
content:”
}
abbr,acronym {
border: 0
}
一般情况下为了避免出现空格什么的都初始化一下*{margin:0pxpadding:0px}然后根据你自己索要的定义进行编写css样式表。当然css有三种写法，一种是写在标签内的，一种是写在head标签下的<style type="text/css"></style>下的，还有一种就是<link>形式的外部css文件的。希望帮助到你
