Use of Bootstrap nav in a page

Ok so I found out what was wrong : it seems that WordPress adds empty p tags into your code. So I had one of those in my HTML and it was messing up the layout.
To tell WordPress to stop doing that, you have to comment this line

 add_filter( 'the_content', 'wpautop' );

which is in default-filters.php in the wp-include directory at the root of your site.
It should work.