surely whats happening is when youre changing youre color or background preferences its also changing your overall display settings including texts...
blocks seen by others are nothing but font type which doesnt matches their installed fonts...
i used to have those blocks and question marks unless once i realised all those boxes disappeared after i installed almost all the fonts available in teh world
ڤ <- this to me appears as arabic text i am sure to others it would seem different on their browsers..
my best bet is that you should set your font type to arial verdana or something which is installed in almost everyones pc so they wont be seeing any boxes
