h5bp/html5-boilerplate — comment on commit aa0396eae757c9e03dda4e463fb0d4db5a5f82d7
File:  line 0
By phobia:

Interesting technique! One thing to be aware with this approach is that it in practise disables the option to have margins in ```em``` on the object where the ```.ir```-class is applied. Not a deal breaker, but sensible to keep in mind. :) In such cases one could of course resort to ```rem``` where supported.

What about prefixes for the text-shadow?