Undecided questions
if ur friends' relatives passed away .what can u say in this situation ???

You can say "I'm sorry for your loss."

You would say: "I am sorry to hear that your uncle/aunt etc passed away. Is there anything I can do to help you?"
If you are sending a sympathy card you would write: I was sorry to hear that your .........
passed away. Please accept our sincere sympathy on this sad occasion Then write your name underneath.

It doesn't get any better than what Jura said above. If I don't know the person that well, I say what okaydaniel said, "I'm sorry for your loss."

I think that if you wanna say something that you don't really mean then don't say it, it would be more apreciated to hear what you really feel, sometimes you don't need to say something to let them know you're supporting them