var ua = navigator.userAgent.toLowerCase();
var msIE = ((ua.indexOf('msie') != -1) && (ua.indexOf('opera') == -1) && (ua.indexOf('webtv') == -1)); //Is true when using Internet Explorer


if(msIE) {

 var ul_browse = document.getElementById('nav_header_browse');
 var ul_post = document.getElementById('nav_header_post');


 ul_browse.onmouseover = function() {
  ul_browse.getElementsByTagName('ul')[0].style.display = 'block';
 };

 ul_browse.onmouseout = function() {
  ul_browse.getElementsByTagName('ul')[0].style.display = 'none';
 }

 ul_post.onmouseover = function() {
  ul_post.getElementsByTagName('ul')[0].style.display = 'block';
 };

 ul_post.onmouseout = function() {
  ul_post.getElementsByTagName('ul')[0].style.display = 'none';
 }

}