User blog comment:DaNASCAT/Technical Update: December 11, 2012/@comment-3441771-20121212034223/@comment-4674838-20121214014318

@Starfleet: RGBA color values are supported in most modern browsers. IE9+, Firefox, Chrome, Safari, and possibly some other browsers like Opera. But anyways, out of Wikia's supported browser list, only IE8 fails to render RGBA.

A reasonable web development policy is to only code for a browser's current stable version and the one immediately preceding it. In the case of internet explorer, that would be IE10 and IE9. For example, Google dropped IE8 support for online apps and services last month.

Wikia apparently feels that IE8 is still a reasonable portion of their traffic, so they still support it. But that doesn't mean that you as a user have to follow Wikia's business ethic -- it's not like they pay you :P. Personally I think the "current version + immediately preceding version" policy makes more sense from a development standpoint, so I'd stick to that.