Cannot redirect ouput?????

Hello experts,
I'm testing a program that prints error message to the screen.
I want to redirect the output to a file using >. but the message only prints on screen and not writing to the file,
Any suggestion on what I might try?

ok, I got this part. If I want to redirect error message I should use 2>.
now come to my 2nd question. how do I put the program in the background and redirect the error message to a file?
file.sh & 2>?????????

<filename> 2><path/filename> &

YAY:b::b::b::b::b::b: