Firefox has (and has had for a long time) a config item "gfx.color_management.mode". The values are documented in [1]. But, I cannot find the definition of "tagged graphics" and "rendered graphics" anywhere. It seems reasonable to assume that a .tif file with an embedded color profile is a "tagged graphic", and that a .jpg file without a profile is a "rendered graphic". But what about a .jpg file with an embedded profile? After all .jpg files have EXIF tags and a color profile can be attached as one of the tag values. [1] http://kb.mozillazine.org/Gfx.color_management.enabled