conditional comments
<!--[if IEMobile 7 ]> <html class="ie-mobile"> <![endif]-->
<!--[if lte IE 7]> <html class="ie7"> <![endif]-->
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<!--[if IE 9]> <html class="ie9"> <![endif]-->
<!--[if !IE]><!--> <html> <!--<![endif]-->
<!-- IE 10+ drop conditional comments so -->
<script>
if (/*@cc_on!@*/false) {
document.documentElement.className+=' ie10';
}
</script>