If you have a <select> dropdown list whose contents you are clearing out and updating via a jQuery AJAX call, you may find that Internet Explorer is not recalculating its layout, and so what was once centered now looks left-aligned. A quick solution is to force IE to redraw by adding trivial whitespace after your <select>:

// clear out and re-populate dropdown

	// ... ajax options ...
	success: function(data) {
			$.each(data, function() {
				// .. update your <select> list
			// force redraw.
			$("#my-dropdown").after(' ');