*{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}
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
这就是个风格问题，怎么写都可以。一般来说是重置浏览器有争议的属性，比如边距什么的，再就是设置一些根样式以供其他元素继承，比如body的字体、颜色等，再就是一些公共样式，clearfix清空文档流之类的。当然还有一些高级的技巧，CSS专家也有很多建议，比如《CSS权威指南》作者Eric Meyer的建议是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
}
/* HTML5 display-role reset for older browsers */
article, aside, details, figcaption, figure,
footer, header, hgroup, menu, nav, section {
display: block
}
body {
line-height: 1
}
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
}
