One could argue this is Microsoft's fault, and there's probably some credence to that, but it's kind of beside the point. Far too many sites seem to have been designed on OS X and not tested anywhere else, and it's an obnoxious, lazy, and frankly elitist practice that needs to end.
Another related syndrome are sites designed on professional-grade monitors, with no thought given to how they're going to look on the other 95% of screens. This kind of shit is like engineering a car in California and just assuming it will work well in February in Montreal.