Ajax :: First Function Call On Page Load Always Skipped

Trying to call the same Ajax function twice on initial load of the page, but only the second one executed. I try to load mainpage, and inside mainpage I try to use ajax to load content1.asp to div1 and content2.asp to div2.

Test scenario (based on the Situation below):
- Page loaded, 1st ajax function skipped, 2nd ajax function loaded
- Remarked 1st ajax function, then 2nd ajax function loaded
- Remarked 2nd ajax function, then 1st ajax function loaded
- Moved the 2nd ajax function to above 1st ajax function, the 2nd ajax function is skipped.

Conclusion:
- the 1st ajax function always skipped. But Why? How to ensure both ajax is called upon loading of the page?

Situation:
mainpage.asp
<div id="div1"></div>
<div id="div2"></div>
<script language="JavaScript1.2">
ajax('div1', 'GET', 'page1.asp');
ajax('div2', 'GET', 'page2.asp');
</script>

ajax.js -
function ajax(strDivID, strMethod, strURL){
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}xmlhttp.onreadystatechange=function(){
if (xmlhttp.readyState==4 && xmlhttp.status==200){
document.getElementById(strDivID).innerHTML=xmlhttp.responseText;
}}
xmlhttp.open(strMethod,strURL,true);
if (strMethod="POST"){
xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
}xmlhttp.send();
}