The requirement for Netscape Navigator is because Netscape invented plugins and javascript. Chime is a plugin and these pages make heavy use of javascript.

Microsoft has elected not to provide full plugin nor full javascript support in Internet Explorer (IE). Therefore Protein Explorer will not work with IE.

The inability of Chime to work with IE is not the result of a policy of MDL Information Systems, Inc. (the creators of Chime), but an unavoidable consequence of the fact that Chime is a plugin and Microsoft's decision to support the Netscape plugin protocol only partially.