当后面的IE中有链接时，下拉菜单会消失

<!--[if lte IE 7]>
$(document).ready(function() {
  // lower the z-index to negative to fix the overlapping drop-down menu problem
  // for IE browsers only
  // the check for support of leading white space should give us false for IE 6-8
  if(!jQuery.support.leadingWhitespace){
    $('.post-header').css('z-index', -2);
    $('.container').css('z-index', -2);
  }
});
</script>
<![endif]-->