function checknav(){
	 
var isMSIE = (navigator.userAgent.toLowerCase().indexOf('msie') >= 0) ? true
: false;
if (isMSIE)
{
   var navigatorVersion =
navigator.appVersion.replace(/.*?MSIE\s(\d\.\d).*/g, '$1')/1;
   if (navigatorVersion < 7)
   { 
       document.getElementById('alertNav').style.display="block";
   }
}
 }