Firefox 47+ drops colspan=0 support

The developers of the Firefox browser since its version 47 have silently dropped support for the zero value of the colspan attribute to match the current version of the HTML specification and for consistency with other browsers, developers of which did not manage to implement this useful feature.

The support is not even kept for extensions, even though their user interface in the new WebExtensions API is implemented using web technologies HTML/CSS and it does not matter for such extensions whether other browser support colspan="0".

The colspan="0" attribute, along with rowspan="0", described in the HTML4 standard, allowed to automatically stretch a table cell to full width of its containing table regardless of the factual number of columns and was one of those advanced features that compared Firefox favorably with other browsers and were certainly among those platform-level innovations that Brendan Eich spoke about when talking about switching Opera to the Blink browser-engine based on WebKit.

It was decided to remove the colspan="0" attribute from HTML5 due to that it was only supported by Firefox. At the same time, zero rowspan was kept in the spec because at that moment, it fitted into the rule of having two independent implementations (Firefox and Opera 12). But Opera since its version 15 switched to the Blink engine (the same engine is used in Chrome, Vivaldi, Yandex Browser, etc.), and almost nobody currently use the outdated Opera 12 based on Presto (Opera’s own browser engine), so Firefox is now de facto the only implementation of the zero rowspan, and we are at risk of losing it soon too.

Formally, a feature may be returned to the spec if it gets more implementations (browsers). But after removing it from the spec, the probability of getting more implementations got close to zero, and the request to return it was rejected as expected. The “innovation machine” is certainly running in a wrong direction.