Netscape has problems with XOR. First off, I have never been able to get XOR to work on an image buffer, and could only get XOR to work with images on the screen (Squares and circles don't show up). This causes a lot of problems for Sgraphics. For example, the canvas example does not clear the object being dragged until the mouse is let go. Look at this example with Netscape 3.x. Drag the circle around to see how XOR does not work. If I am missing something, please let me know :-)
Another problem is that filling an image buffer does not seem to work. If you are using Netscape 3.x, notice the white areas where the image buffer did not get filled with gray.
Explorer seems to get the image buffer right, but transparent gifs act strange. The transparent color is not transparent, but seems to be XORing with other colors. Look at this example with Explorer. Place the camera over other objects and look at how the background affects the other object. Again, if I am missing something...