Sometimes we need to add references to scripts, metatags or conditional styles to the WordPress <head></head> section in header.php. WordPress has an action hook for this purpose. It’s very easy to use.
To add scripts, conditional styles or links to header.php, use the wp_head() action hook, like this:
add_action('wp_head', 'function_name');
function function_name() {
echo "\n"; /* New line */
/* function content */
echo "\n"; /* New line */
}
For example, IE9 struggles with CSS gradients so if you use ColorZilla to create a CSS gradient you will need to add a conditional style to wp_head() along with a gradient class (.gradient) to your elements with gradients. To add the style condition to wp_head, do this:
add_action('wp_head', 'ie9_css_gradient_fix');
function ie9_css_gradient_fix() {
echo "\n".'<!--[if gte IE 9]>
<style type="text/css">
.gradient {
filter: none;
}
</style>
<![endif]-->'."\n";
}
Will show you how to add the gradient class in a different post.
