I should be used to this. Really, I should. It is just SO easy to make bad assumptions about Microsoft software when you are coding. Take MSXML6 ... please! (That's my best Dangerfield, I swear!) They added a XMLHttpRequest class, which Netscape has supported forever. My inherited Learning Management System has this conditional:
Now, this code is just there to help determine if the ActiveX control should be used, but of COURSE the original developer leaned on it later for all SORTS of stuff. So, when MSXML6 came out, with its juicy new XMLHttpRequest object, the conditional assumed Mozilla, and, well, hilarity ensued.