Payment showing up in email but not on account balance?

I just sold my iPhone 4 on craigslist for $400 but for shipping he have me $500(lives in Nigeria) and on my email it says I got the money but on my account balance it says $0.00!

Do not send the phone until it clears to your account. Never deal with anyone in Nigeria, usually is a scam.
I sell on ebay and that country is top of my exclusion list.

You got scammed. Nigeria is the scam capital of the world. Just google Nigerian scam and have a look. The email you got saying you were paid but your money wouldn't be released until you showed proof of shipment was fake.

It's a fake email. The scammer is trying to convince you that he/she has paid so you will mail them the phone for free.

It's a scam - read this article from 2008 that explains how it works
http://consumerist.com/2008/10/30/how-a-nigerian-steals-your-laptop/
Those emails are always fake. Forward to spoof@paypal.com
If he really paid the money would have appeared in your account before you got the email. You don't get any email from paypal until the money appears in your account. Also Paypal will NEVER ask you to ship an item and get a tracking number before the transaction appears
Not to mention, Paypal prohibits All transactions with Nigeria due to scams like this.

I don't know why people choose to ignore Craigslist's very clear scam warnings page where they specifically warn users to ONLY deal with people they can meet face to face, NEVER give out Paypal details to anyone and AVOID All transactions involving shipping http://www.craigslist.org/about/scams

Change your Paypal address As soon as possible if it's not too late. In addition to stealing your phone, these scammers also use password hacking software to try and hack your account

Craigslist is ONLY for face to face CASH transactions or you are always going to be scammed. Paypal will either be a spoofed email or from a hacked account. Checks and money orders will be fake. Remember YOU are the seller and YOU set the terms of the sale. Never let a buyer tell you how they are paying you or how they will get the phone. You accept cash only and always meet in a public, well-lit location of your choice (library, coffee shop, bank, hotel lobby, mall food court, etc)

Relist your phone and put in the ad across the top and bottom something like
CASH ONLY, LOCAL BUYERS ONLY, NO SHIPPING, NO EXCEPTIONS

I'm actually surprised you only had one scammer contact you. Last time I listed a phone I had 4 scammers in 24 hours try to get me to send to Nigeria

Oh, and ignore the future threats. Once they know you aren't sending the phone, they are going to send you fake emails from 'Paypal' or a 'lawyer' or 'police' or 'FBI' threatening you with a lawsuit or arrest if you don't send the phone or send the money back through Western Union/Moneygram. Ignore all of them - it's all part of the scam. It follows the same script. And be prepared to be spammed - I once responded to a scammer and started getting up to 200 spam messages a day once they knew I didn't fall for the scam