Posts on my website are running very slowly (up to 22 seconds to load a post). See my website: http://www.alternatieva.com/vakblad/ What could be the cause of this and what can I do about it? Thank you!
Try disabling all of your plugins and see if that improves the single post loading. If it doesn't, then it may be a function internal to your theme. I looked at your document type, and thought it was strange looking. What does Facebook, specifically FBML, have to do with your Html. And there is a reference to OpenGraphProtocol: <html xmlns="http://www.w3.org/1999/xhtml" dir="ltr" lang="nl-NL" xmlns:og='http://opengraphprotocol.org/schema/' xmlns:fb='http://www.facebook.com/2008/fbml'> Code (markup): Not sure what this does to the rendering of the page, it may be nothing to do with page loading. But anytime I see a Facebook app integrated into a website, the site tends to render a little slower.
You have too much images, according to pagespeed, though you already minified the script, but try to avoid using too much images, unless you host them in CDN.. If you must, don't forget to compress them before you upload them..