Drupal HTML.tpl.php file won't effect site? My aim is to allow zooming in and out in mobile devices in my responsive Drupal 7 site. I have followed a Drupalize.me video and some more documentation that teach how to allow it via my theme's HTML.tpl.php and added the marked row there (Image attached), yet nothing happened. Maybe it should go to the system's HTML.tpl.php instead? maybe there is something to apply at the Drupal UI so that the site would be affected? P.S - I've cleared the Drupal cache.
There are several ways to achieve this. 

You could hand code the meta viewport tag in your html template file as you did. The proper tag may need to be used as shown below:

&lt;meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes"&gt;


You could also use a page alter to add the html to your page as shown below (place in theme template.php):

function YOURTHEMENAME_page_alter($page) {
  // Viewport array, change values in content below.
  $viewport = array(
    '#type' =&gt; 'html_tag',
    '#tag' =&gt; 'meta',
    '#attributes' =&gt; array(
      'name' =&gt;  'viewport',
      'content' =&gt;  'width=device-width, initial-scale=1.0, user-scalable=yes'
    )
  );
  // Drupal add HTML head.
  drupal_add_html_head($viewport, 'viewport');
}


Or you could use the viewport module

Note: Do not alter the system html template file, puppies will die!