Safari and Firefox have the same level of support for HTML5 sequence elements (after viewing your demo page, I assume these are the elements you are talking about): they can be styled, but you must set display: block; implicitly.
aside, article, section { display: block; }
Adding this rule to your CSS will help solve the problem.
To make these elements stylish in IE, you just need to use HTML5 shim / shiv. Add the following HTML to your <head> :
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