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I can confirm that this bug occurs in the OS X version of Firefox. It doesn't happen in safari, though.
I can also confirm that the line-terminator on OS X is the *nix \n, rather that Windows \r\n or MacOS 9 and below \r.

The Python script Paul Tooke Posted above works for me, by the way.

More stuff:
Gun
x = 8, y = 91, rule = 45678/27/3
3.AB$2.B.ABA$3.A3.B$2.A.2A$.B.5A$2.5A$7A$.6A$.5A.B$.4A.A$B.2A$.2A.B$
3.A$2.B$2.AB$3.A60$3.A$2.AB$2.B$3.A$.2A.B$B.2A$.4A.A$.5A.B$.6A$7A$2.
5A$.B.5A$2.A.2A$3.A3.B$2.B.ABA$3.AB!

Huge breeder
x = 419, y = 246, rule = 45678/27/3
305.BA$305.BA$304.BA$11 ...

Quadratic + Sierpinski breeder:

p8:
x = 13, y = 10, rule = B017/S01
3b5o$3b5o2$2o$2o6bo$8bo2b2o$11b2o2$5b5o$5b5o!

EDIT: Smaller p8:
x = 9, y = 10, rule = B017/S01
b2o4b2o$b2o4b2o$7b2o2$5bo$3bo2$2o$2o4b2o$2o4b2o!

The period of the replicator shuttle can be changed by moving the pair of blinkers farthest from the replicator ...

p20 gun:
x = 13, y = 11, rule = B017/S01
5b3o$5b3o3$2o2bo$2o2bo4$10b3o$10b3o!
Adding a 2x2 block converts the gun into a higher period two-barrel gun:
x = 24, y = 11, rule = B017/S01
5b3o$5b3o$22b2o$22b2o$2o2bo$2o2bo4$10b3o$10b3o!
Moving the block over by four cells makes it an even higher ...

Replicator shuttles (p16, p32, p112):
x = 55, y = 54, rule = B017/S01
20bo9bo2$20bo9bo$bo2bobobo$23bo$bo2bo18bo2$bo2bobobo$23bo$bo2bo3bo14bo
2$bo2bobo13bo9bo2$20bo9bo7$20bo21bo2$20bo21bo$bobobo2bobobo$23bo$5bo6b
o10bo2$bobo4bobobo$23bo$5bo2bo14bo2$bobobo2bobobo7bo21bo2$20bo21bo7$
20bo33bo2$20bo33bo ...

Period-2144064 oscillator for #1: