<link rel="stylesheet" type="text/css" href="<?php echo $your_plugins_url; ?>css/your_css_file.css" />
While technically it is possible to include files using HTML script and link tags on a standalone site, they are not best practice on a WordPress site. The main benefits of using WordPress’s core functions instead of generic HTML are:
- Files are included to the generated page at the right time according to the script dependencies.
- Files will only be included if it has not been already included and if all the dependencies have been registered.
- Script localization is very easy, just call wp_localize_script() on your included files. Check out Script Localization with JQuery in WordPress for more information.