var http = false;

if(navigator.appName == "Microsoft Internet Explorer") {
  http = new ActiveXObject("Microsoft.XMLHTTP");
} else {
  http = new XMLHttpRequest();
} 

function replace(changeurlinfo) {

  http.open("GET", changeurlinfo+"ajax=1;", true);
  http.onreadystatechange=function() {
    if(http.readyState == 4) {
      document.getElementById('txtcont').innerHTML = http.responseText;
    }
  }
  http.send(null);
}