how to locate a line of code appearing on the site?

Hi Andrew, thank you so much for your reply. The whole thing is offline, on localhost, because as I am a beginner I am not confident to do it in the real website, so I am not sure how could I show you, nor I see how can I send a screenshot.
All I can say is that I have been customizing an already custom template and at some point, I didnt notice, this line started to appear at the bottom of the content in every page.

I did modifications in files header, functions, style following several tips for different things I have been trying out. Now I want to finally export the whole new thing and cannot have this line removed.
I am not so OK with applying a code to hide those warnings, cause I suppose they have a reason to appear.. but don’t know where this comes from!

UPDATE:
WP_DEBUG is already set to ‘false’ in my config file, so that means this is not a php notice? What is this actually? I don’t even know how to call what I am looking for…. 🙁

HI Andrew,
no, I don’t have any caching plugin.

Weeks ago I followed a tutorial on how to create a new menu area, which I have done to create a Header menu. The code inserted looks fine, since now wordpress indeed shows it.

It took me so much work to figure out how to create a menu for that area that I am not ok with the idea of deleting this piece of code which was inserted in functions.php file. I am afraid of messing the whole thing but I will give a try, since apparently there is no way to know the source of this line… I don’t even know what it means, but thanks!

nonon, this does not appear anywhere! that is my problem! I don’t know where it comes from!

It is not written in any of the files (cause I search ALL) and it appears on my frond end, at the bottom of every content area of every page.

The only thing related to ‘header menu’ I have done was to create and register such an area, following a tutorial, I have inserted

function register_my_menu() {
register_nav_menu(‘header-menu’,__( ‘Header Menu’ ));
}
add_action( ‘init’, ‘register_my_menu’ );

This have indeed created this option of menu, that is all. now I have this appearing written in all my pages. And I have not noticed before, so I don’t know what have cause this to appear.

And if I go in functions and delete this, the menu are will disappear and everything I put there will disappear, I suppose..

I have now tried to selected this text and right click ‘view page source’. There I see:

<div id=”comments”>

</div><!– #comments –>

<?wp_nav_menu( array( ‘theme_location’ => ‘header-menu’, ‘container_class’ => ‘header_menu_class’ ) ); ?>

</div><!– #content –>
</div><!– #container –>

So, that means this is a comment? But what is generating this comment? and How to remove it?

Hi Andrew, thank you very much I will follow that lead, I will post back if I solve as it might help other beginners! Greetings from Berlin!

Great idea1 yes, I have just changed and the line disappear. Back to my customized template, it is showing there in every page… I am reading the posts regarding php tags to see if I understand first before messing up even more.