Artist artwork on the iPhone 4s?

As you can see from the picture, I'm missing the artist artwork from Britney Spears, this is the only one I'm missing and I have no idea why.
I have album art for Britney, Blur, Bon Jovi and Blink 182 and I have the artist artwork for all of them except Britney and I'm at a loss as to why.
Any help you can give will be much appreciated.
Thanks in advance.
Artist artwork on the iPhone 4s

You will need to sync your device to your computer and transfer your music over to your computer with iTunes, after doing so pick the song you want, then right click it and it will have a number of options one saying if you would like the artwork to the song, it will search the Web and find the artwork for it, if they can't find the art work it's because the song isn't labeled correctly, such as < Album name, track number, song name, artist name, etc. > if anything is missing or incorrect it won't find the art