检测浏览器是否支持AJAX

 <script type="text/javascript">
 function ajaxFunction()
 { var xmlHttp;
 try { // Firefox, Opera 8.0+, Safari
 xmlHttp=new XMLHttpRequest();
  }
 catch (e)
 { // Internet Explorer
 try {
 xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
  }
 catch (e) {
 try {
 xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
 } catch (e) {
 alert("您的浏览器不支持AJAX！");
 return false;
 }
 }
 }
 }
 </script>