No dark grey line in Konqueror 4.8.4 or Chromium 20 here, but Firefox 13.0.1 does mess it up like he says. (EDIT: browser versions added, OS is 64-bit Arch Linux)<p>From a practical standpoint I guess you should be careful around `transparent` if you're a designer, but the moral responsibility clearly falls on browser vendors here. It's not meaningful to talk about the "colour" of transparent objects, and using those values when doing anti-aliasing (however technically appealing) is wrong.<p>I think the problem is that they're doing the anti-aliasing "too early". They're not blending the colours you see, they're blending the colours they're painting as they paint them.
This jsfiddle demonstrates it a bit more clearly.<p><a href="http://jsfiddle.net/liamnewmarch/GgUV2/" rel="nofollow">http://jsfiddle.net/liamnewmarch/GgUV2/</a><p>The top gradient is from transparent to red, the bottom is from rgba(255, 0, 0, 0) to red.<p>Notice how the top gradient fades through grey - this is because 'transparent' is a synonym for rgba(0, 0, 0, 0).<p>What the parent article picks up on, is how this is visible via Firefox's antialiasing.
I see no link to a relevant bug report linked in the article and without one, that bug is never going to get fixed.<p>A bug report with a minimal testcase would take 50% the time it took to write the article itself but actually have greater impact.
> As it stands, many, <i>many</i> things use transparent black when they shouldn't.<p>Transparent is transparent. Some code might be lazy and calculate colors based on only three of four color channels but that is a bug and will be fixed.
I see dark grey line between the triangles on Firefox 15 beta3 Windows XP Home 32bit<p>Maybe this is hardware dependent? I do not have any hardware acceleration that I am aware of - integrated i3 graphics.
Firefox 14.0.1, Windows 7 x64. Grey line is visible for a split second as page loads then disappears. EDIT: well now this is bizarre - it disappears and reappears as I scroll.
RGBA can be unintuitive. Opera implemented transitions by interpolating them (I think it's solved now), which turns out not to work very well: <a href="http://bugs.hawn.be/opera/transitions/color/" rel="nofollow">http://bugs.hawn.be/opera/transitions/color/</a>