The point I was trying to make, is that your output will be unreliable because you have shoddy code.
We can't troubleshoot what causes the problems, because we don't know what effects your crappy code edits are having.
So first, you need to fix the code that we know causes problems. Once that is fixed we can move on.....
Like I said, unclosed elements will definitely throw IE for a loop,.
Upon investigating your site, it seems your single post view doesn't use the h1 tag which is unclosed. Only your index does. So I will defer to my original post. Validate your code. Close your h1
</div><!-- #branding --> will probably do wonders
Your index page has many more errors than your single page..... not a coincidence