1、user agent stylesheet是浏览器默认样式表，是浏览器默认样式。
2、不同浏览器的默认样式不同个，甚至同种浏览器不同版本的默认样式也可能不同。其中google中对body的默认样式为margin：8px；
3、前端开发者在开发网页的时候如果考虑适配不同浏览器的不同默认样式，一般是采用重置浏览器的默认样式
例如：
html{height:100%; width:100%;}
a{text-decoration:none;}
li{list-style:none;}
4、收集的PC端重置样式
@charset "utf-8";
/* CSS Document */
* { color:#444; }
body { font:12px/1.5 "微软雅黑",Arial,Tahoma, Helvetica,\5b8b\4f53, sans-serif; }
html,body,div,h1,h2,h3,h4,h5,h6,hr,p,blockquote,dl,dt,dd,ul,ol,li,pre,form,fieldset,object,code,em,span,var,legend,button,input,textarea,th,td,a,img,header,footer,nav,aside,audio,datalist,section { margin:0;padding:0;border:0;outline:0; }/*清除内外边距*/
h1,h2,h3,h4,h5,h6 { font-weight:normal;font-size:100%; }/*设置默认字体*/
:focus { outline:0; }
ul,ol,ul li,ol li { list-style: none; }/*重置列表*/
address,caption,cite,em,code,dfn,th,var { font-style:normal;font-weight:normal; }
form label { cursor:pointer; }
input,button,select,textarea { font-family:inherit;font-size:100%;outline:none; }
textarea { resize:none }
input { vertical-align:middle; }
img { border:0; }/*重置图片元素*/
table { border-collapse:collapse;border-spacing: 0; }/*重置表格*/
.l { float:left; }
.r { float:right; }
button,input[type="reset"],input[type="button"],input[type="submit"] { line-height:normal !important; }
a { text-decoration:none;}
a { color:#666;}
a:hover { text-decoration:underline; }
input { _filter:chroma(color=#000000); }
/*--清除浮动
------------------------------------------------------------------------------------------*/
.clearfix:after { clear:both;content:".";display:block;font-size:0;height:0;visibility:hidden; }
.clearfix:after { _zoom:1; }
.overflow { overflow:hidden; _zoom:1; }
.clear { clear:both; height:0;font-size:0; overflow:hidden; }
5、移动端重置样式reset.css
@charset "utf-8";
/* @group Public */
body,div,ul,ol,dl,li,dt,dd,h1,h2,h3,h4,p,form,iframe,input,textarea,a,span,em,strong,img,html,nav,header,article,button,footer,var {padding:0;margin:0;}
body { font:12px/1.2rem "Microsoft YaHei",tahoma,arial,sans-serif;min-width:320px;position:relative; }
form,input {background:none;border:none;}
ul,dl,ol {list-style-type:none;}
h1, h2, h3, h4, h5 { font:12px/1.2rem "Microsoft YaHei",arial,tahoma; }
a { text-decoration:none; }
a:hover,a:focus { outline:none; }
table { border-collapse:collapse;border-spacing:0; }
img { border:none; }
strong,b { font-weight:normal; }
em,i,var { font-style:normal; }
p { text-indent:0; }
.clear { clear:both;height:0;line-height:0;overflow:hidden;width:0; }
.clearfix:after { clear:both;content:".";display:block;font-size:0;height:0;visibility:hidden; }
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作者：可乐6666
来源：CSDN
原文：https://blog.csdn.net/xuexizhe88/article/details/76900659
版权声明：本文为博主原创文章，转载请附上博文链接！