Why does our website load so much slower in IE than any other browser?

Question

We have a WordPress website which loads sufficiently in every browser I've tried, except for IE. For some reason in IE, it seems to freeze the browser for a few seconds every single time the page is loaded, doubly so if it has to load a page with an iframe of another page. The user has to wait awhile before they can interact with anything on the page.

Here's the site.

Someone suggested we could use WP Supercache to solve the issue, but I've had problems with this plugin in the past and am reluctant to rely on it, especially since this seems to be only a problem in IE.

What is the best way I can troubleshoot this issue? How do I find out which scripts in the header, or footer, etc. is causing it? Is there a quick way to do so, or do I just need to start eliminating variables within the theme?

Answer 1

Thanks to this thread I just found, the answer appears to be fancybox: Fancybox causing slow load times in IE?

Specifically, the IE-specific filters in the CSS file for fancybox. I removed those filter styles, and it loads fine now.

Answer 2

I'd don't quite understand why but in IE9 style.css is being pushed right down the page load order - see request #35 http://www.webpagetest.org/result/130327_Y9_f1d5796658d8475b68e2e537644173f1/1/details/

As a browser won't render until it's downloaded the applicable CSS this blocks rendering.

Chrome on the other hand prioritises downloads so that resources that can block rendering are downloaded ahead of images.

Here's a side-by-side video of the two loading experiences.

(If you want help looking at this further my contact details are in my profile)

Answer 3

Sorry, I don't seem to be able to give just a comment. Anyway, in Opera 12.14 it works fine. And in Explorer (8) it works just as well, no errors in the console. Just my .1 cent.