You applied width to the links with the .adminmenu a
rule, which doesn't work because <a> elements are inline elements by default. Inline elements treat box model properties quite a bit differently from block elements, and one of the biggest differences is width and height properties don't apply to inline elements.
IE, of course, is going against the grain here where the standard is conserned, whereas Firefox and other browsers are following the standard to the letter. Luckily, it's pretty easy to fix, just add display: block;
to your .adminmenu a
rule for <a> elements, and that will change the <a> element from an inline to a block element, at which point Firefox, Safari, Opera, etc, will allow you to apply width or height.
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