CSS Hack
1. google和safari （webkit内核）
@media screen and (-webkit-min-device-pixel-ratio:0){}
2.firefox（Gecko内核）
/* 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) {}
/* Firefox 3+ */
@-moz-document url-prefix(){}
3.opera（Presto内核）
/* Opera 7 */
@media all and (min-width: 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) {}
4.ie（）
/* IE 6/7 */
@media screen\9 {}
/* IE 6/7/8 */
@media \0screen\,screen\9 {}
/* IE 8 */
@media \0screen {}
/* IE 8/9/10 & Opera */
@media screen\0 {}
/* IE 9/10, Firefox 3.5+, Opera */
@media screen and (min-resolution: +72dpi) {}
/* IE 9/10 */}
/* IE 10+ */
@media screen and (-ms-high-contrast: active), (-ms-high-contrast: none) {}
/* Everything but IE 6/7/8 */
@media screen and (min-width: 400px) {}
JS Hack
1.google
var isChrome = Boolean(window.chrome);
2.safari
/* Safari */
var isSafari = /a/.__proto__=='//';
3.firefox
/* 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';
4.opera
/* Opera 9.64- */
var isOpera = /^function \(/.test([].sort);
/* Opera 12- */
var isOpera = Boolean(window.opera);
5.ie
/* IE <= 8 */
var isIE = '\v'=='v';
/* 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 */
(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;