Hello,
I'm setting up Montezuma after having used Atahualpa for over a year.
I'd like to center header image logo, tagline on top of menu.

Here is the website http://meetitalia.com/en/

I've followed different posts in the forum and have used the following code for header.php

<div id="logo-img" class="col12 row">
	<a href="<?php echo home_url(); ?>">
        <img src="http://meetitalia.com/en/wp-content/uploads/sites/2/2013/01/meetitalia_532x113@72.png" >  </a>
</div>
<div id="banner-bg" class="cf">
	<div id="banner" class="row">
		<div id="logo-area" class="col5">
			<p id="tagline">Welcome to Italy</p>
          	<p id="tagline">Discover Italian Culture through Arts, Cuisine, History and Language Courses</p>
		</div>
		<?php wp_nav_menu( array( 
			'container' => 'nav', 
			'container_class' => 'menu-wrapper col7', 
			'container_id' => 'menu1-wrapper', 
			'menu_id' => 'menu1', 
			'menu_class' => 'cf menu', 
			'theme_location' => 'menu1', 
			'fallback_cb' => 'bfa_page_menu' 
		) ); ?>
	</div>
</div>
<div id="breadcrumbs1-bg">
	<nav id="breadcrumbs1" class="breadcrumbs lw">
		<?php bfa_breadcrumbs( 'breadcrumbs1' ); ?>
	</nav>
</div>

you have added a row and then said the banner should take two columns of that row. (all rows should have a total of 12 columns) Since there is nothing else in the row, the logo will shows starting at the left.

you need to add a div before and after your div so the row adds up to 12 coluns.

oh and you shouldn't have a class of 'row' with classes of 'colx' on the same div unless you were using 'col12'

Originally Posted by meetatahualpa

I'd like to center header image logo, tagline on top of menu.

If you really mean centered, style the containing div as text-align:center; and the contained image as display:inline.

If you want to have it all left aligned, but more toward the center, use the css grid system.