If scripting is supported: there should be only a single static jumble below with the word "Control" blinking steadily. If there are two squares, or if the square is animated, then the test has failed.

If scripting is unsupported: there should be two identical patterned squares below.

1
222222222
3 444 55555555 66666 777777777 
############
#AA1       #
#AA        #
#B222222222#
#BCDEEF3   #
# C EE444  #
# C55555555#
# C66666   #
# C        #
#777777777 #
#          #
############ Control