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

For those who have avoided this in the past, it's probably because of an old IE5 bug. It considers font-size:0 to be 1px. This is fixed in IE5.5 (but possibly still affected IE5/Mac?). There's also a Mozilla bug that relates to this, fixed in 2002. https://bugzilla.mozilla.org/show_bug.cgi?id=89503

Thankfully both of those are but a distant memory today!