below is a simple javascript to tell you how to call web service with parameter

var WebReq = null;

function findZip() {
       if (window.XMLHttpRequest)
                WebReq = new XMLHttpRequest();
       else if (window.ActiveXObject) {
                  if (new ActiveXObject("Microsoft.XMLHTTP"))
                       WebReq = new ActiveXObject("Microsoft.XMLHTTP");
                  else
                       WebReq = new ActiveXObject("Msxml2.XMLHTTP");
                  }

var url = "http://xxxxxx/getCityState";
WebReq.open("post", url, true);
WebReq.setRequestHeader("Host","localhost:2508/IVA");
WebReq.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
WebReq.setRequestHeader("Content-Length","100");
WebReq.onreadystatechange = Result;
}