var browserName=navigator.appName; 

 if (browserName=="Microsoft Internet Explorer")
 {
  document.write("<link href=\"http://www.a-1networks.com/library/nav.css\" rel=\"stylesheet\" type=\"text/css\" />");
 }
 else
  {
    document.write("<link href=\"http://www.a-1networks.com/library/nav1.css\" rel=\"stylesheet\" type=\"text/css\" />");
   }