When we use "asynchronous to false" in ajax request following happens::
As shown in example below:
xmlhttp.open("GET","ajax_info.txt",false);
xmlhttp.send();
document.getElementById("myDiv").innerHTML=xmlhttp.responseText;
Here, after send() method,browser stops & control never goes to next statement "document.getElementById("myDiv").innerHTML=xmlhttp.responseText;" unless & untill Server Response is recieved by ajax.