腾讯
body,ol,ul,h1,h2,h3,h4,h5,h6,p,th,td,dl,dd,form,fieldset,legend,input,textarea,select{margin:0;padding:0}
body{font:12px "宋体","Arial Narrow",HELVETICA;background:#fff;-webkit-text-size-adjust:100%}
a{color:#172c45;text-decoration:none}
a:hover{color:#cd0200;text-decoration:underline}
em{font-style:normal}
li{list-style:none}
img{border:0;vertical-align:middle}
table{border-collapse:collapse;border-spacing:0}
p{word-wrap:break-word}
百度
body,h1,h2,h3,h4,h5,h6,hr,p,blockquote,dl,dt,dd,ul,ol,li,pre,form,fieldset,legend,button,input,textarea,th,td{margin:0;padding:0}
html{color:#000;overflow-y:scroll;overflow:-moz-scrollbars-vertical}
body,button,input,select,textarea{font-size:12px;font-family:arial,'Hiragino Sans GB','Microsoft Yahei','微软雅黑','宋体',\5b8b\4f53,Tahoma,Arial,Helvetica,STHeiti}
h1,h2,h3,h4,h5,h6{font-size:100%}
em{font-style:normal}
small{font-size:12px}
ul,ol{list-style:none}
a{text-decoration:none}
a:hover{text-decoration:underline}
legend{color:#000}
fieldset,img{border:0}
button,input,select,textarea{font-size:100%}
table{border-collapse:collapse;border-spacing:0}
img{-ms-interpolation-mode:bicubic}
textarea{resize:vertical}
.left{float:left}
.right{float:right}
.overflow{overflow:hidden}
.hide{display:none}
.block{display:block}
.inline{display:inline}
.error{color:#F00;font-size:12px}
label,button{cursor:pointer}
.clearfix:after{content:'\20';display:block;height:0;clear:both}
.clearfix{zoom:1}.clear{clear:both;height:0;line-height:0;font-size:0;visibility:hidden;overflow:hidden}
.wordwrap{word-break:break-all;word-wrap:break-word}
pre.wordwrap{white-space:pre-wrap}
body{text-align:center}
body,form{position:relative}
td{text-align:left}
img{border:0}
新浪
/* 初始化CSS */
html, body, ul, li, ol, dl, dd, dt, p, h1, h2, h3, h4, h5, h6, form, fieldset, legend, img { margin:0; padding:0; }
fieldset, img { border:none; }
img{display: block;}
address, caption, cite, code, dfn, th, var { font-style:normal; font-weight:normal; }
ul, ol { list-style:none; }
input { padding-top:0; padding-bottom:0; font-family: "SimSun","宋体";}
input::-moz-focus-inner { border:none; padding:0; }
select, input { vertical-align:middle; }
select, input, textarea { font-size:12px; margin:0; }
input[type="text"], input[type="password"], textarea { outline-style:none; -webkit-appearance:none; }
textarea { resize:none; }
table { border-collapse:collapse; }
body { color:#333; padding:5px 0; font:12px/20px "SimSun","宋体","Arial Narrow",HELVETICA; background:#fff;/* overflow-y:scroll;*/ }
.clearfix:after { content:"."; display:block; height:0; visibility:hidden; clear:both; }
.clearfix { zoom:1; }
.clearit { clear:both; height:0; font-size:0; overflow:hidden; }
a { color:#666; text-decoration:none; }
a:visited { color:#666; }
a:hover, a:active, a:focus { color:#ff8400; text-decoration:underline; }
淘宝
body, h1, h2, h3, h4, h5, h6, hr, p, blockquote, dl, dt, dd, ul, ol, li, pre, form, fieldset, legend, button, input, textarea, th, td { margin:0; padding:0; }
body, button, input, select, textarea { font:12px/1.5tahoma, arial, \5b8b\4f53; }
h1, h2, h3, h4, h5, h6{ font-size:100%; }
address, cite, dfn, em, var { font-style:normal; }
code, kbd, pre, samp { font-family:couriernew, courier, monospace; }
small{ font-size:12px; }
ul, ol { list-style:none; }
a { text-decoration:none; }
a:hover { text-decoration:underline; }
sup { vertical-align:text-top; }
sub{ vertical-align:text-bottom; }
legend { color:#000; }
fieldset, img { border:0; }
button, input, select, textarea { font-size:100%; }
table { border-collapse:collapse; border-spacing:0; }
转自：https://www.cnblogs.com/staven/p/4818459.html