function userCheck(f)
{
    var user = f.username.value;
    var xhr = getXMLHttpRequest();
	
    xhr.open('POST','ajax/usercheck.php',true);
       xhr.onreadystatechange = function()
    {
		if (xhr.readyState == 4)
        {
			if (document.getElementById)
		    {
				var what = xhr.responseText;
				if(what == "1")
					document.getElementById('usercheck').innerHTML = '<img src="/images/10.png">Username valid';
				else if(what == "0")
					document.getElementById('usercheck').innerHTML = '<img src="/images/12.png">Username already in use';
				else if(what == "2")
					document.getElementById('usercheck').innerHTML = '<img src="/images/12.png">Username format invalid';	
		    }			
        }
    }
    xhr.setRequestHeader('Content-type','application/x-www-form-urlencoded');
    var data = 'user='+escape(user);
    xhr.send(data);
}

function emailCheck(f)
{
    var email = f.email.value;
    var xhr = getXMLHttpRequest();
    xhr.open('POST','ajax/emailcheck.php',true);
    xhr.onreadystatechange = function()
    {
		if (xhr.readyState == 4)
        {
			if (document.getElementById)
		    {
				var what = xhr.responseText;
				if(what == "1")
					document.getElementById('mailcheck').innerHTML = '<img src="/images/10.png">Email valid';
				else if(what == "0")
					document.getElementById('mailcheck').innerHTML = '<img src="/images/12.png">Email already in use';
				else if(what == "2")
					document.getElementById('mailcheck').innerHTML = '<img src="/images/12.png">Email invalid';	
		    }			
        }
    }
    xhr.setRequestHeader('Content-type','application/x-www-form-urlencoded');
    var data = 'email='+escape(email);
    xhr.send(data);
}

function getXMLHttpRequest() {
        var xhr = null;
 
        if(window.XMLHttpRequest || window.ActiveXObject) {
                if(window.ActiveXObject) {
                        try {
                                xhr = new ActiveXObject("Msxml2.XMLHTTP");
                        } catch(e) {
                                xhr = new ActiveXObject("Microsoft.XMLHTTP");
                        }
                } else {
                        xhr = new XMLHttpRequest();
                }
        } else {
                alert('JavaScript : your browser does not support XMLHttpRequest...');
                return null;
        }
 
        return xhr;
}