css中hack的原理

/*****  Selector    Hacks   ******/

/*  IE6 and below   */

* html #uno {   color:  red }

/*  IE7 */

*:first-child+html  #dos {  color:  red }

/*  IE7, FF,    Saf, Opera */

html>body #tres { color: red }

/*  IE8, FF, Saf, Opera (Everything but IE  6,7) */ html>/**/body #cuatro { color:  red }

/*  Opera 9.27 and below, safari 2 */

html:first-child #cinco { color: red }

/*  Safari  2-3 */

html[xmlns*=""] body:last-child #seis   {   color:  red }

/* safari 3+, chrome 1+, opera9+, ff 3.5+ */

body:nth-of-type(1) #siete  {   color:  red }

/* safari 3+, chrome 1+, opera9+, ff 3.5+ */

 body:first-of-type #ocho { color:  red }

/* saf3+, chrome1+ */

@media screen   and (-webkit-min-device-pixel-ratio:0) {    #diez { color:  red } }

/* iPhone / mobile webkit */

@media screen and (max-device-width: 480px) {

 #veintiseis { color: red }

 }

/*  Safari  2   -   3.1 */

 html[xmlns*=""]:root #trece { color: red }

/* Safari 2 - 3.1, Opera 9.25 */

 *|html[xmlns*=""]  #catorce { color: red }

/* Everything but IE6-8 */

 :root *> #quince { color: red }

/*  IE7 */

 *+html #dieciocho { color: red }

/* Firefox only. 1+ */

 #veinticuatro, x:-moz-any-link { color: red }

/*  Firefox 3.0+ */

#veinticinco, x:-moz-any-link, x:default { color: red }