Conditional Stylesheets on Drupal 8

This module allows you to add "conditional-stylesheets" in a much simpler
manner, by adding lines to your theme's.info.yml file. The syntax for that is:

conditional-stylesheets:
 EXPRESSION:
   MEDIA:
     css/style.css

where

• EXPRESSION can be any of the "downlevel-hidden" expressions specified in: About Conditional Comments
• MEDIA can be any of the normal CSS media keywords

For example, to add a stylesheet that only targets IE 6 and below, use:

conditional-stylesheets:
  lt IE 7:
    all:
      css/ie6-and-below.css

To add a print stylesheet for IE9 only, use:

conditional-stylesheets:
  IE 9:
    print:
      css/ie9.css

And to add a print stylesheet for all version of IE, use:

conditional-stylesheets:
  IE:
    print:
      css/ie9.css

Placing the above lines in your theme's .info file will automatically append the following HTML code after your existing stylesheets in the <head> of your website.

<!--[if lt IE 7]>
  <link type="text/css" rel="stylesheet" media="all" href="css/ie6-and-below.css" />
<![endif]-->
<!--[if IE 9]>
  <link type="text/css" rel="stylesheet" media="all" href="css/ie9.css" />
<![endif]-->
<!--[if IE]>
  <link type="text/css" rel="stylesheet" media="print" href="css/ie9.css" />
<![endif]-->

*** IMPORTANT ***

Drupal 8 stores a cache of the data in .info.yml files. If you modify any lines in
your theme's .info.yml file, you MUST rebuild Drupal 8's cache. Use "drush cr" to clear the cache if Drush is installed.