The AcidTest doesn't deal with profiles and color fidelity as far as I know - it has more to do with following the standards for rendering even more basic elements of pages, animation, etc. Sadly, only the Webkit rendering engine passes the test and follows the standards: another feather in Apple's cap.
I may have been a little unclear about profiles. One can attach a profile - and one can convert it to a different profile.
For the web, it's best to convert the image to sRGB, then perform adjustments. You can make a separate copy for that purpose if you like.
Attaching a profile is only going to work if people view your images in browsers that are profile-aware. Most people's browsers are not profile-aware.
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