This is Taylors answer from the website below
Taylor: This is kind of a popular question because on my album cover, I have this tattoo on my foot, of a heart. What most people don't know is that it is a henna tattoo and it's not real. It will be though, if my album goes double platinum. It's a pact that me, my friends, and my family all have made. We will all get a tattoo of a heart on our foot if my album goes double platinum. I definitely want that to happen, so go out and buy lots and lots of CDs, so that maybe that will happen sooner than later.
Scroll down and find the video clip that has the title
Is Taylors Tattoo real?
I hope this helps!