Tumblr issues in IE9

I've been creating a custom Tumblr blog theme for my site and all was going good until I tried viewing in IE9...

http://bantros.tumblr.com

Tested in newest versions of Chrome, Firefox and Opera and my blog looks the same and as expected whilst I was working on it, needless to say I got a huge surprise when I checked in IE9 and didn't know what to ma开发者_开发问答ke of it.

I am using HTML5 and I double checked the code to see if I made a mistake or two, W3C Validator comes up with a few errors but nothing notable.

In my frustration I ended up inserting- <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> and it makes it all nice again. This can't be a solution though, I must've done something wrong. Any help or tips would be great, thanks.

NB. I've taken out the Chrome Framework for now so you can see what I mean

It looks fine in IE9 right now.

The most likely problem is that your page was somehow in Quirks Mode.

That would make the page look utterly broken in IE.

To verify if this was the problem, open your page in IE, and hit F12 to bring up the Developer Tools. Try changing the "Document Mode", especially to "Quirks mode", and see if it matches the broken look you had before.