/* check for Internet Explorer */ 
var isIE  = (navigator.appVersion.indexOf("MSIE") != -1) ? true : false;

function testForIE6(){
 /* display ie6 warning */
 if (navigator.userAgent.indexOf("MSIE 6.0")!=-1){
  alert("You are using Internet Explorer version 6.0 which is known to have compatibility issues with most modern websites.  Please use a newer browser to ensure the best possible experience.");
 }
}