What is this dark line running down my belly called? Is it normal? Will it go away?

It's called the linea nigra. It's a white line between your belly button and pelvis which you probably never noticed until you became pregnant. It starts to darken around week 23 of pregnancy. Other parts of your body will also start to darken, like your areola. It will also fade after you give birth. Mine has lightened again! http://www.whattoexpect.com/pregnancy/symptoms-and-solutions/linea-nigra.aspx