HN user
Take a look at my comment below. Page elements and untagged images are rendered on the full display gamut. If you have a wide gamut display, like my 30" Dell, everything looks super saturated.
The correct behavior would be to interpret all page elements and untagged images as being in the sRGB color space. This is what the W3C recommends and Firefox follows.
This is precisely the reason why I still use Firefox. It's impossible to use Chrome on wide gamut displays, everything looks oversaturated. http://cameratico.com/guides/web-browser-color-management-gu...
Chrome now supports ICC profiles for images, but still fail to color manage page elements, which is a deal breaker for me.
I agree 100% with you: always tag your images.
Firefox doesn't assume sRGB for untagged images and graphs by default, only if you configure it on the advanced menu: http://gearoracle.com/guides/firefox-color-management/
The point of the test is to encourage browser developers to give users choices on how untagged page elements are color managed, and the right choice is to consider then in sRGB space. Firefox is the only browser that allows this via the gfx.color_management.mode switch. This is important because not all page graphics are images and there's no way to tag a CSS element, for example.
The idea of the last test is to compare how the browser renders untagged images and page elements. On a wide gamut display, the untagged elements will be over-saturated, unless you're using Firefox and have it properly configured to assume sRGB on untagged elements.