I am working on a website which works fine in Chrome and Firefox but doesn’t display right in Internet Explorer (all versions). Here’s what it looks like in all three browsers:

Chrome and Firefox

Internet Explorer
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There is a space between your DOCTYPE and your html that is preventing IE from applying a proper DOCTYPE declaration. The DOCTYPE needs to be in the absolute top of your document with no spaces. Remove that and your page should work fine.
You can see the error [here] in the validation report
Important bit: