The Blogger/Blogspot Navbar is a default feature that appears at the top of every Blogger powered blog. It looks similar to this:
If you wish to hide this (so it is no longer visible at the top of your blog) then here's what you do.
Log into your dashboard, go to Template -> Edit HTML. Anywhere between <head> and </head> tags, and after a } bracket you need to insert the following code:
#navbar-iframe {height: 0px;
}
This will reduce the Navbar height to zero, thus removing the Navbar.