Text suddenly appeared above header

My site’s been working fine, until I visited just now and there’s a rogue white bar appeared above the header image with the words “page contents” inside it. Be very grateful if someone could advise me how to get rid of it (and perhaps explain why it’s appeared). My site’s at lovefowey.net.
I’m an FTP newbie so if that’s involved idiot-proof instructions would be much appreciated.
Thanks in advance.