Mozilla has fixed an 18-year-old bug in Firefox, numbered Bug 290125.

Bug 290125 was first reported on April 12, 2005, just a few days before Firefox 1.0.3 was released. This issue has to do with Firefox rendering text with the ::first-character CSS pseudo-element, and the submitter indicated that the Gecko engine used by the browser ignores any declared line-height and inherits the line-height of the parent box. At the time, Opera 7.5+ and Safari 1.0+ both handled this correctly.

The following screenshot shows the specific manifestation of this error:

In fact, this issue originally only appeared on the Mac version of Firefox, after the developers discovered that it handled line height differently than Firefox on other platforms. And Firefox 3.0, released in 2002, fixed the bug. But in 2014, the question was reopened again. At the time the CSS Working Group pointed out that Firefox’s special handling of line heights did not comply with the CSS specification and caused compatibility issues. This caused some sites with large initials in text blocks (such as The Verge and The Guardian) to render incorrectly in Firefox compared to other browsers.

However, the issue has been classified as low priority, so progress has been very slow, and it will not be marked as fixed until December 20, 2022. Firefox 110 will include the updated code. The latest stable version of Firefox is currently 108, and 110 is expected to be released in February 2023.