function unhide(divID) {
	var item = document.getElementById(divID);
	var texts = document.getElementById('messageDiv');
	if (item) {
		item.className=(item.className=='hidden')?'unhidden':'hidden';
		texts.className=(texts.className=='hidden')?'unhidden':'hidden';
	}
}

function swapCard(card) {
	var swap = document.getElementById('postcard');
	if (swap) {
		swap.src = "_img/postcard_"+card+".png";
		document.sendCard.postcard.value = card;
	}
}

function checkEmail(emailAddress){
	var re = new RegExp("^[a-zA-Z0-9-'\+~]+(\.[a-zA-Z0-9-'\+~]+)*@([a-zA-Z_0-9-]+\.)+[a-zA-Z]{2,7}$");
	return emailAddress.match(re);
}

function checkForm(){
	var yName = document.getElementById('your_name').value;
	var yEmail = document.getElementById('your_email').value;
	var tName = document.getElementById('their_name').value;
	var tEmail = document.getElementById('their_email').value;

	if((!checkEmail(tEmail)) || (!checkEmail(yEmail))){
		alert('Please enter valid a valid email address');
		return false;
	}else if(!tName.length){
		alert('Please enter their name');
		return false;
	}else if(!yName.length){
		alert('Please enter your name');
		return false;
	}else{return true;}	
}