ajax在firefox中可以正常执行，ie6,傲游中不能执行

  var request = false;

try {
request = new XMLHttpRequest();
} catch (trymicrosoft) {
try {
request = new ActiveXObject("Msxml2.XMLHTTP");
} catch (othermicrosoft) {
try {
request = new ActiveXObject("Microsoft.XMLHTTP");
} catch (failed) {
request = false;
}
}
}
可能是什么原因呢？ie中完全不好用

---

测试代码：
demo01.php
PHP code:

<script src="demo02.js"></script>
<form>
<input type=button value="ok" onclick="a()">
</form>


demo02.js
JScript code:
\
var request = false;

try {
request = new XMLHttpRequest();
} catch (trymicrosoft) {
try {
request = new ActiveXObject("Msxml2.XMLHTTP");
} catch (othermicrosoft) {
try {
request = new ActiveXObject("Microsoft.XMLHTTP");
} catch (failed) {
request = false;
}
}
}


if (!request)
alert("页面异常，请刷新后重试");


function a() {

var url = 'demo03.php';

request.open("GET&quo