To hide the Blogger Navbar :
1- Log in to blogger
2- On your Dashboard, select Layout. This will take you to the Template tab. Click Edit HTML. Under the Edit Template section you will see you blog's HTML.
3- paste the CSS definition in the top of the template code:
...
<b:skin><![CDATA[/*
-----------------------------------------------
Blogger Template Style
Name: Rounders
Designer: Douglas Bowman
URL: www.stopdesign.com
Date: 27 Feb 2004
Updated by: Blogger Team
----------------------------------------------- */
#navbar-iframe {
display: none !important;
}
/* Variable definitions
====================
<Variable name="mainBgColor" description="Main Background Color"
type="color" default="#fff" value="#ffffff">
<Variable name="mainTextColor" description="Text Color" type="color"
default="#333" value="#333333">
...
Remove the code to show it again.
Step by step in video: