"NPH Scripts", by defintion, are scripts whose headers go unparsed by the server. In other words, the contents of these scripts go out directly to the browser without the usual CGI involvement by the server to parse the headers the script generates and formulate the CGI script's response into a valid HTTP response.

So if you build your script right, there should be no compatibility problems at all between it and any browser. If a normal CGI script has no problems with IE, and your NPH version of the same script does, you've done something wrong. Generally NPH scripts are only useful if you need greater control over MIME types (such as with multipart replies, and even then this might work with standard CGI), or you want to override certain server behavior.

There is a compatibility issue with IE in that it does not handle multipart HTTP responses by the server. Things like multipart/x-mixed-replace are unsupported. That is frequently the most common use for NPH scripts, so I'm guessing that's what you were talking about.