function validate_email() {
	var sender_email = document.user_email.sender_email.value;
	var email_filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
	if (email_filter.test(sender_email)) {
		send_email();
	} else {
		alert('Please enter a valid email address');
	}
}

function send_email() {
	var form = document.user_email;
	var sender_name 	= form.sender_name.value;
	var sender_email 	= form.sender_email.value;
	var sender_message 	= form.sender_message.value; 
	var instance_id		= form.instance_id.value;
	
	var http_request = false;
	var request_url = '/lpc/app/pages/shared/email_response.php';
	if (window.XMLHttpRequest) { // Mozilla, Safari
		http_request = new XMLHttpRequest();
	} else if (window.ActiveXObject) { // IE
		try {
			http_request = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e) {
			try {
				http_request = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (e) {}
		}
	}
	if (!http_request) {
		alert('An error has occured.');
		return false;
	}
	document.getElementById('email_loading').style.display = "block";
	document.getElementById('email_form').style.display = "none";
	
	var post_header = 'sender_name='+sender_name+'&sender_email='+sender_email+'&sender_message='+sender_message+'&instance_id='+instance_id;
	
	http_request.onreadystatechange = function() { updatePage(http_request); };
	http_request.open('POST', request_url, true);
	
	http_request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");
	http_request.send(post_header);
	return true;	
}

function updatePage(http_request) {
	if (http_request.readyState == 4) {
		if (http_request.status == 200) {
			var response_content = http_request.responseText;
			document.getElementById('email_loading').style.display = "none";
			document.getElementById('email_form').innerHTML = response_content;
			document.getElementById('email_form').style.display = "block";
		} else {
			alert('There was a problem with the request. Please try again');
			document.getElementById('email_loading').style.display = "none";
			document.getElementById('email_form').style.display = "block";
		}
	}
}