Stereo & Electronics - HELP! Headunit not working

Hoping you can help me here guys. Put a new battery in my g/f's car...03 sentra SE-R spec V...little rice mobile but its ok for her. Anyway, after i get everything hooked back up....no power to the had unit. Nothing happens. I pulled the fuse box and checked fuses and theyre fine. Where should I look next?

Is EVERYTHING else working? You might have popped a main fuse.
I would pull the back of the radio out and test for +12V there.
If you dont have voltage there keep following the wire untill you do.