Microsoft blocking pages to Firefox users?

I have run into a few pages over at Microsoft that have not loaded from time to time in Firefox, and really did not think anything about it. Apparently it is getting the dandruff up of some of the Firefox development team. I am not all that surprised, but I would be curious to have a technical explanation on why they will not load or are they simply and truly being blocked? If someone can answer that question I think that would explain a lot on why it is happening. [weblogs.mozillazine.org/asa/]