Apple's iTunes music store marked its 10 billionth song download today – the same day that Apple CEO Steve Jobs turns 55.

As predicted, the countdown meter on the iTunes Web site hit 10 billion just before 5 p.m. ET today.

The person who downloaded the 10 billionth song will receive a $10,000 iTunes gift card, courtesy of Apple. Neither the lucky downloader nor the milestone song has been revealed yet.

It has been just under seven years since the iTunes store started selling music. Since that time, the iPod and iTunes have overtaken and revolutionized the portable music business and sold a boatload of songs.

iTunes has made Apple an unbelievable amount of money. If every song purchased cost $1, which is a low estimate considering there are many that cost more, Apple has made $10 billion off of this one part of its business structure in seven years. And that's not taking into consideration the songs that cost more than $1 as well as all the TV shows and other media that are purchased through the iTunes Store.

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