When creating a WordPress theme don’t forget to include a wp_head(); call in the HTML HEAD section of your theme. It’s very simple to do, just include:
Before the closing HEAD tag (</head>) in your HTML.
Why make such a fuss over a single function call? Because it does a fair bit of work behind the scenes and without it some WordPress features will not work properly. Take a look at the wp_head section of the wp-includes/default-filters.php file in WordPress, you’ll see a number of events that are tied to the wp_head action.
One area where this is a particular problem is for offline blog clients that make use of the XML-RPC and AtomPub APIs in WordPress. The “Really Simple Discoverability” (RSD) link that WordPress inserts instructs these clients on where to find the RSD URL, which contains information on how the clients can send XML-RPC and AtomPub requests. We’ve seen a number of times now where an error reported by a WordPress iPhone App user is caused because there is no RSD link in their WordPress blog. Looking a little deeper reveals that there was no RSD link because the theme they were using didn’t include a call to wp_head().
If you are writing a WordPress theme here is your reminder, make sure that the wp_head() function is being called at the end of your HEAD section.