Supported browser features

features.txt

box-sizing supported by: <bit.ly/HM42F3>
  Chrome, IE 8+, Firefox (-moz), Safari 5.1+, Opera
  iOS <= 4 & Android <= 2.3 (-webkit), Firefox (-moz)

:before and :after pseudo-elements supported by:
  Chrome, IE 8+, Firefox, Safari, Opera 4.0+:
::before and ::after pseudo-elements supported by:
  Chrome, IE 9+, Firefox, Safari, Opera 7.0+:
<mzl.la/Q5hf09> <bit.ly/YCpGPd> <bit.ly/XV046x>

XHTML supported by IE 9+ and all other browsers

media queries supported by: <mzl.la/Ykdnuw>
  Chrome, IE 9+, Firefox, Safari 1.3+, Opera 9.2+

flexible box layout supported by: <bit.ly/e4JYg3>
  Chrome, IE 10+, Firefox, Safari, Opera 12.1+

Google has dropped support for IE 9: <bit.ly/z6LWk0>
jQuery 2.0 will drop support for IE 8: <bit.ly/QQ0Cme>