var http = false;

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

function check(user) {
  http.abort();
http.open("GET", "checkyahoo.php?id=" + user, true);
  http.onreadystatechange=function() {
	if(http.readyState == 1) {
	  document.getElementById('result').innerHTML = '<img src="images/loading.gif" />';
	}
	if(http.readyState == 4) {
	  document.getElementById('result').innerHTML = http.responseText;
	}
  }
  http.send(null);
}