function lookup_username(username)
{
	var xmlhttp;
	try
	{
		xmlhttp=new XMLHttpRequest();
	}
	catch (e)
	{
		try
		{
			xmlhttp=new ActiveXObject("Msxml2.XMLHTTP");
		}
		catch (e)
		{
			try
			{
				xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
			}
			catch (e)
			{
				return false;
			}
		}
	}

	var url='/register/index.php?lookup=true&username='+username;
	xmlhttp.onreadystatechange=function()
	{
		if (xmlhttp.readyState==4)
		{
			document.getElementById('usernames').innerHTML=xmlhttp.responseText;
		}
	}
	xmlhttp.open("GET",url,true);
	xmlhttp.send(null);
}