of out "rm -rf ~/.mozilla" ..........
what do" ~/."sign stand for???

~/ = The current user's home directory, for example if you are user "jed" then it's likely:
/home/jed
If you are user root, it's likely:
/root

And . means a hidden file/directory

Cool

Just to add to that, the shell expands '~' to /home/user and '/' indicates a directory when it isn't just the 'root' of the file system. And '.' means the file is 'hidden' even if you can see it - most file managers and such seem to default to showing the files so it might not make much sense to call them 'hidden' when you can see them all over the place, but they are.

Which is pretty much what MasterC said, except that you can type 'cd ~' to cd to home without the '/' - those are separable components. (You can type 'cd', too, but y'know...)

So anyway:

quote :
Just to add to that, the shell expands '~' to /home/use
end quote

Not necessary : "~" means your home directory root ($HOME env. variable )

Regards