I have added the next to my <head>:

<link rel="stylesheet" type="text/css" media="all and (min-width: 481px) and (max-width: 1024px)" href="<?php bloginfo('template_directory'); ?>/css/tablet.css" />`

For that primary page that is header.php, it's working fine. But when Time passes to allows say: http://mysyte.com/products-page/checkout/ after checking with firebug I can tell the browser didnt even loaded this file even when I designated lots of qualities for that page within this file (tablet.css).

What else could you suggest, where you can search for the issue? Thanks!

P.S. platform - wordpress and ecommerce wordpress wordpress plugin.

Perhaps you have attempted echoing the bloginfo function for example...

<link rel="stylesheet" type="text/css" media="all and (min-width: 481px) and (max-width: 1024px)" href="<?php echo bloginfo('template_directory'); ?>/css/tablet.css" />`