常见class关键词：
布局类：header, footer, container, main, content, aside, page, section
包裹类：wrap, inner
区块类：region, block, box
结构类：hd, bd, ft, top, bottom, left, right, middle, col, row, grid, span
列表类：list, item, field
主次类：primary, secondary, sub, minor
大小类：s, m, l, xl, large, small
状态类：active, current, checked, hover, fail, success, warn, error, on, off
导航类：nav, prev, next, breadcrumb, forward, back, indicator, paging, first, last
交互类：tips, alert, modal, pop, panel, tabs, accordion, slide, scroll, overlay,
星级类：rate, star
分割类：group, seperate, divider
等分类：full, half, third, quarter
表格类：table, tr, td, cell, row
图片类：img, thumbnail, original, album, gallery
语言类：cn, en
论坛类：forum, bbs, topic, post
方向类：up, down, left, right
其他语义类：btn, close, ok, cancel, switch; link, title, info, intro, more, icon; form, label, search, contact, phone, date, email, user; view, loading...
制定简单规则：
以中划线连接，如.item-img
使用两个中划线表示特殊化，如.item-img.item-img--small表示在.item-img的基础上特殊化
状态类直接使用单词，参考上面的关键词，如.active, .checked
图标以icon-为前缀（字体图标采用.icon-font.i-name方式命名）。
模块采用关键词命名，如.slide, .modal, .tips, .tabs，特殊化采用上面两个中划线表示，如.imgslide--full, .modal--pay, .tips--up, .tabs--simple
js操作的类统一加上js-前缀
