Being a part of linux community I feel obliged to share with you the solution I have discovered. I have solved my headache with below (quote):
On 2004-11-03, damon <> wrote:
> It appears that my sh is actually just a link to /bin/bash. Altering
> permissions has not made any difference. Must I install sh?
No; bash *IS* sh, for all practical purposes. When invoked as "sh" instead
of "bash" it restricts itself to behaving like sh.
Now, how are you trying to run the installer? Are you doing something
like "./firefox-installer.sh" or are you explicitly telling sh to run it,
e.g. "sh ./firefox-installer.sh"?