function getInternetExplorerVersion()  // Returns the version of Internet Explorer or a -1 (indicating the use of another browser).
{
	var rv = -1; // Return value assumes failure.
  	if (navigator.appName == 'Microsoft Internet Explorer')
  	{
   		var ua = navigator.userAgent;
    	var re  = new RegExp("MSIE ([0-9]{1,}[\.0-9]{0,})");
    	if (re.exec(ua) != null)
      		rv = parseFloat( RegExp.$1 );
  	}
  			
  	return rv;
}
			
function checkVersion()
{
	var msg = "You're not using Internet Explorer.";
  	var ver = getInternetExplorerVersion();

  	if ( ver > -1 )
  	{
    	if ( ver < 8.0 ) 
    	{
      		msg = "This page is best viewed on Internet Explorer version 8 or higher.\nYou are currently using version " + ver + " .";
      	
      		alert( msg );
      	}
  	}
}