Well, for one, your post in the iOS games thread (W3C validation) contains a link with a bad href attribute. A valid one should be surrounded in quotes (href="http://chooseyourstory.com"), but in yours, there is no ending quote, so a portion of the document is mistaken for the URL, which in turn leads to both missing and unclosed tags.
If posting links is what causes the issue, remember to ensure the URLs are enclosed in quotes.