CSS优先级、引入方式、Hack

优先级

important > 内联(1,0,0,0) > id(1,0,0) > class(1,0) > element(1) > *通配符

css引入方式

方式一：在head里用link标签(推荐使用)
<link rel="stylesheet" href="xxx.css">

方式二：在head里用style标签
<style> some css </style>

方式三：内联，在标签上用style
<div style=" some css "></div>

方式四：@import
@import url("xxx.css");

link和@import的区别：
1.兼容性：@import在IE5+支持，link全部支持
2.DOM样式操作：link（可被js改变），@import（不可被js改变）
3.加载顺序：@import必须放在最顶部，和link混用时破坏并行加载，link阻断@import，多个@import不同于预期加载顺序

 Hacks

转自：梦想天空

IE选择器 Hack

/* IE 6 and below */
* html .selector  {} 
.suckyie6.selector {} /* .suckyie6 can be any unused class */

/* IE 7 and below */
.selector, {}

/* IE 7 */
*:first-child+html .selector {} 
.selector, x:-IE7 {} 
*+html .selector {}

/* Everything but IE 6 */
html > body .selector {}

/* Everything but IE 6/7 */
html > /**/ body .selector {}
head ~ /* */ body .selector {}

/* Everything but IE 6/7/8 */
:root *> .selector {} 
body:last-child .selector {} 
body:nth-of-type(1) .selector {} 
body:first-of-type .selector {}

IE属性/值 Hack

/* IE 6 */
.selector { _color: blue; } 
.selector { -color: blue; }

/* IE 6/7 - acts as an !important */
.selector { color: blue !ie; } 
/* string after ! can be anything */

/* IE 6/7 - any combination of these characters: 
 ! $ & * ( ) = % + @ , . / ` [ ] # ~ ? : < > | */
.selector { !color: blue; } 
.selector { $color: blue; } 
.selector { &color: blue; } 
.selector { *color: blue; } 
/* ... */

/* IE 8/9 */
.selector { color: blue/; } 
/* must go at the END of all rules */

/* IE 8/9 */
.selector { color: blue/; } 
/* must go at the END of all rules */

/* IE 9/10 */
.selector:nth-of-type(1n) { color: blue9; }

/* IE 6/7/8/9/10 */
.selector { color: blue9; } 
.selector { color/***/: blue9; }

/* Everything but IE 6 */
.selector { color/**/: blue; }

IE Media Query Hack

/* IE 6/7 */
@media screen9 {}

/* IE 8 */
@media screen {}

/* IE 9/10, Firefox 3.5+, Opera */
@media screen and (min-resolution: +72dpi) {}

/* IE 10+ */
@media screen and (-ms-high-contrast: active), (-ms-high-contrast: none) {}

/* IE 6/7/8 */
@media screen\,screen9 {}

/* IE 8/9/10 & Opera */
@media screen {}

/* IE 9/10 */
@media screen and (min-0) {}

/* Everything but IE 6/7/8 */
@media screen and (min- 400px) {}

IE Javascript Hack

/* IE 6 */
(checkIE = document.createElement("b")).innerHTML = "<!--[if IE 6]><i></i><![endif]-->"; 
var isIE = checkIE.getElementsByTagName("i").length == 1;

/* IE 7 */
(checkIE = document.createElement("b")).innerHTML = "<!--[if IE 7]><i></i><![endif]-->"; 
var isIE = checkIE.getElementsByTagName("i").length == 1;
navigator.appVersion.indexOf("MSIE 7.")!=-1

/* IE <= 8 */
var isIE = 'v'=='v';

/* IE 8 */
(checkIE = document.createElement("b")).innerHTML = "<!--[if IE 8]><i></i><![endif]-->"; 
var isIE = checkIE.getElementsByTagName("i").length == 1;

/* IE 9 */
(checkIE = document.createElement("b")).innerHTML = "<!--[if IE 9]><i></i><![endif]-->"; 
var isIE = checkIE.getElementsByTagName("i").length == 1;

/* IE 10 */
var isIE = eval("/*@cc_on!@*/false") && document.documentMode === 10;

/* IE 10 */
var isIE = document.body.style.msTouchAction != undefined;

Firefox 浏览器

选择器Hack

/* Firefox 1.5 */
body:empty .selector {}

/* Firefox 2+ */
.selector, x:-moz-any-link {}

/* Firefox 3+ */
.selector, x:-moz-any-link; x:default {}

/* Firefox 3.5+ */
body:not(:-moz-handler-blocked) .selector {}

媒体查询 Hack

/* Firefox 3.5+, IE 9/10, Opera */
@media screen and (min-resolution: +72dpi) {}

/* Firefox 3.6+ */
@media screen and (-moz-images-in-menus:0) {}

/* Firefox 4+ */
@media screen and (min--moz-device-pixel-ratio:0) {}

Javascript Hack

/* Firefox */
var isFF = !!navigator.userAgent.match(/firefox/i);

/* Firefox 2 - 13 */
var isFF = Boolean(window.globalStorage);

/* Firefox 2/3 */
var isFF = /a/[-1]=='a';

/* Firefox 3 */
var isFF = (function x(){})[-5]=='x';

Chrome浏览器

选择器 Hack

/* Chrome 24- and Safari 5- */
::made-up-pseudo-element, .selector {}

媒体查询 Hack

/* Chrome, Safari 3+ */
@media screen and (-webkit-min-device-pixel-ratio:0) {}

Javascript Hack

/* Chrome */
var isChrome = Boolean(window.chrome);

Safari浏览器

选择器Hack

/* Safari 2/3 */
html[xmlns*=""] body:last-child .selector {} 
html[xmlns*=""]:root .selector  {}

/* Safari 2/3.1, Opera 9.25 */
*|html[xmlns*=""] .selector {}

/* Safari 5- and Chrome 24- */
::made-up-pseudo-element, .selector {}

媒体查询Hack

/* Safari 3+, Chrome */
@media screen and (-webkit-min-device-pixel-ratio:0) {}

Javascript Hack

/* Safari */
var isSafari = /a/.__proto__=='//';

Opera浏览器

选择器Hack

/* Opera 9.25, Safari 2/3.1 */
*|html[xmlns*=""] .selector {}

/* Opera 9.27 and below, Safari 2 */
html:first-child .selector {}

/* Opera 9.5+ */
noindex:-o-prefocus, .selector {}

媒体查询Hack

/* Opera 7 */
@media all and (min- 0px){}

/* Opera 12- */
@media all and (-webkit-min-device-pixel-ratio:10000), not all and (-webkit-min-device-pixel-ratio:0) {}

/* Opera, Firefox 3.5+, IE 9/10 */
@media screen and (min-resolution: +72dpi) {}

/* Opera, IE 8/9/10 */
@media screen {}

Javascript Hack

/* Opera 9.64- */
var isOpera = /^function (/.test([].sort);

/* Opera 12- */
var isOpera = Boolean(window.opera);