I don't believe the web browsers are color managed - at least the are unable to render an Adobe RGB. Chrome isn't either.
I've even seen some cases where images are rendered inaccurately enough with sRGB that they need to be re-edited for use on the web with all of these browsers plus IE. (My image in the Landscape Challenge voting for this month is the problem image. It had to be re-edited for the color to come close to my JPEG on my calibrated laptop.)