function postRequest(strURL){
                    var xmlHttp;
                    if(window.XMLHttpRequest){ // For Mozilla, Safari, ...
                         var xmlHttp = new XMLHttpRequest();
                    }
                    else if(window.ActiveXObject){ // For Internet Explorer
                         var xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
                    }
                    xmlHttp.open('POST', strURL, true);
                    xmlHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
                    xmlHttp.onreadystatechange = function(){
                         if (xmlHttp.readyState == 4){
                              updatepage(xmlHttp.responseText);
                         }
                    }
                    xmlHttp.send(strURL);
               }
               
               function updatepage(str){
                    document.getElementById('result').value = str;
               }
               
               function callMultiply(){
                    var a = parseInt(document.f1.a.value);
                    var b = parseInt(document.f1.b.value);
                    var url = "multiply.php?a=" + a + "&b=" + b + "";
                    postRequest(url);
               }