相信如果您动手写过网页的话，应该体会到有些标签会自带一些默认的样式，而这些样式或许又是我们不想要的，所以我们可以用以下代码清除所有标签的默认样式
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;
}