Specle soft preview requires that your browser supports colour management. Colour management is only supported on up-to-date browsers. In addition some browsers only support colour mangement on certain image types. Specle uses PNG as it supported colour accurately on most browsers and does not use lossy compression.
All of these browsers support colour management - in order of level of colour management support:
The test image below uses a mix of unusual ICC version 4 and version 2 profiles, one for each quadrant of the image
Profiles in each quadrant: v4 e-sRGB v4 YCC-RGB
v2 GBR v2 Adobe RGB
The display of the above test image on your system will change according to the abilities of your system. Here are three possible outcomes. (These are RGB screenshots from actual systems)
The test and image were provided by Lars Borg, Adobe Systems, November 2003. The embedded profiles are provided by Adobe Systems. GBR is a Green-Blue-Red color space.