if (jQuery.browser.msie && jQuery.browser.version == "6.0") {
  alert ("This is less than IE7");
} else {
  alert ("This is greater than IE7");
}

if ((window.XMLHttpRequest == undefined) && (ActiveXObject != undefined)) {
    	alert ("This is not IE6");
       } else {
    	alert ("This is greater than IE6");
       }