Teacher Discussion Forums

I'm typing 'mojibake' in Japanese below:
文字化け
I'm sure it's illegible to most of you if you do not have a Japanese system installed on your computer.
What do you call this phenomenon?
1. garbage characters
2. changed characters
3. garbles (garbled characters; garbling)
4. ghost characters
5. gobbledygook
6. mis-coded characters
7. random characters
8. scramble
9. strange characters
10. stupid characters
11. unreadable characters
12. any other?

People who experience problems with the Japanese text that I sent them usually report back along these lines:

I can't read it; My PC can't display it/can't handle Japanese characters
It's just (come out as) a load of nonsense/garbage/crap/junk

So, 1. and 11. from your list come the closest. (Not sure we'd use 'illegible', at least not with its "correct" meaning).

I just got 4 question marks instead of the usual gobbledygook.