The so-called hack is that only a specific browser can recognize this hack code. Hack is not a good thing, unless there is no way, we try not to use the thing. The following is a list of CSS Hack for each browser.
Firefox browser
@-moz-document Url-prefix () { . selector { property:value; }}
Browsers that support all Gecko kernels (including Firefox)
*>.selector {property:value;}
Webkit Kernel Browser
@media screen and (-webkit-min-device-pixel-ratio:0) { Selector { property:value; }}
Opera Browser
Html:first-child>b\ody Selector {property:value;}
Internet explorer
Internet Explorer has a different hack approach for different versions.
IE 9
: Root Selector {property:value\9;}
IE 9-
Selector {property:value\9;}
IE 8
Selector {property:value/;} Or: @media \0screen { Selector {property:value;}}
IE 8+
Selector {property:value\0;}
IE 7
*+html Selector{property:value;} Or: *:first-child+html Selector {property:value;}
IE 7-
Selector {*property:value;}
IE6
Selector { _property:value;} Or: *html Selector { property:value;}
Browser CSS Hack Collection