function validateUsername(){
	var username = document.getElementById('username').value;
	
	if(username != null && username != ''){	
		UserClient.validateUsername(username, function(usernameExists){
			if(usernameExists == false){
				document.getElementById('usernamemessages').style.fontSize = 'xx-small';
				document.getElementById('usernamemessages').innerHTML = 
					'This username is already in use';
				document.getElementById('submit').disabled = true;
				document.getElementById('username').style.backgroundColor = '#FF8888';
			}else{
				document.getElementById('usernamemessages').style.fontSize = 'medium';
				document.getElementById('usernamemessages').innerHTML = '';
				document.getElementById('submit').disabled = false;
				document.getElementById('username').style.backgroundColor = '#9FEF9F';
			}
		});
	}else{
		document.getElementById('usernamemessages').style.fontSize = 'medium';
		document.getElementById('usernamemessages').innerHTML = '';
		document.getElementById('username').style.backgroundColor = 'white';
		document.getElementById('submit').disabled = false;
	}
	return false;
}