The error is noticed when visiting the Most Loved, Dreaded, and Wanted Tools page and switching to the "Most Wanted" tab. The first two results (Android and Javascript) do not appear correctly in Firefox. See below:
This is because the CSS rules that define the widths for these two bars are incorrect:
.bar-set.super-wanted ul li.super-android {
width: 17.7%%;
}
.bar-set.super-wanted ul li.super-android span {
left: 17.7%%;
}
.bar-set.super-wanted ul li.super-javascript {
width: 15.4%%;
}
Note that the percentage symbol appears twice for each of these values. Apparently, Chrome doesn't care about this and just removes the second symbol and treats it as a percentage. But Firefox, on the other hand, treats this error as an invalid value and completely drops the entire property, so no width gets applied at all and the bar expands to a 100% width - it's default behavior.