Hi there,
What version of the plugin are you using? The latest versions of the plugin already enqueue the stylesheet via WordPress API functions so it should validate.
I’m using WordPress Popular Posts 2.3.5 with WordPress 3.5.2
The link looks like this:
<link rel="stylesheet" href="/wp-content/themes/my-childtheme/wpp.css?ver=3.5.2">
Ah, I see. I’ll take a look at this later today. Thanks for the notice!
Quick update: just checked on my local test blog and this is what WordPress outputs for me:
<link rel="stylesheet" id="wordpress-popular-posts-css" href="http://localhost/test_wp/wp-content/themes/twentytwelve/wpp.css?ver=2.3.5" type="text/css" media="all">
For me, the stylesheet gets appended correctly, no missing type
parameter either.
I also noticed in your reply that the stylesheet has a relative path instead of a absolute path, which leads me to believe that this is hardcoded into your theme.
Also, you mentioned that it was in your wp_footer – WPP includes the stylesheet in wp_head, not in wp_footer. Did you mean wp_head?