Due to changes in the postmeta API, my HeadMeta plugin had a compatibility problem with some recent versions of WordPress. The problem appeared when there was only one postmeta value (either a ‘head_meta’ or ‘head_link’ entry) associated with a post. If you had multiple entries, or used the ‘keywords’ shortcut, the problem did not appear.
HeadMeta 1.4 fixes this problem, and also adds a ‘description’ shortcut for generating a description <meta> tag. It also fixes a bug which would generate an empty ‘keywords’ <meta> tag, even when no keyword metadata was associated with the post.
If you aren’t already familiar with HeadMeta, it’s a simple plugin which allows you to add <meta> and <link> tags to the <head> segment of individual posts or pages, usually for SEO purposes. There are other plugins which do much more, but this one is small, and doesn’t try to get terribly complicated. All data is managed via the ‘Custom Fields’ section of the post/page editing screen in WordPress.