This is driving me CRAZY!!

When my phone is on the 'lock screen' it says that I have 1 new email.

I only have one gmail account set up on my phone, and I went through my gmail on my computer to make sure everything was marked as read, and it is. I also pulled the battery hoping that would clear it, but it didn't. So why wont this notification go away?! It only appears on my lock screen... there is no email notification once you go into the phone.

Can anyone help??