Doesn't work on all browsers

[The Little Guy]

Why doesn't this work on all browsers?

 

<script type="text/javascript">
function disImage(){
var ajaxRequest;  // The variable that makes Ajax possible!

try{
	// Opera 8.0+, Firefox, Safari
	ajaxRequest = new XMLHttpRequest();
} catch (e){
	// Internet Explorer Browsers
	try{
		ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
	} catch (e) {
		try{
			ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
		} catch (e){
			// Something went wrong
			alert("You Browser Doesn't support AJAX.");
			return false;
		}
	}
}
// Create a function that will receive data sent from the server
ajaxRequest.onreadystatechange = function(){
	if(ajaxRequest.readyState == 4){
		document.getElementById('replaceImage').innerHTML = ajaxRequest.responseText;
	}
}
ajaxRequest.open("GET", "/incl/image", true);
ajaxRequest.send(null);	
}
</script>

[The Little Guy]

Forgot some more stuff:

 

HTML:

Can't read this? <a onclick="javascript:disImage();" href="javascript:disImage();">Try Another</a>
<p id="replaceImage">
<img class="borderGray" src="/images/image" alt="Random Image" />
</p>

 

image.php:

<img class="borderGray" src="/images/image" alt="Random Image" />