Fixing my registration page: HTTP shows twice and adding text.

For some reason, on my registration page, in the Blog URL field, "http" is showing up twice. Have a look see:
I need to fix that.

Also, I want to add just a short bit of text: Where it says "Blog URL (required)" I would like to add something like "You may register and map your own domain once you have registered"

Can someone please help?