function checkValue(fld) { 
	if (fld.value == 'your email address') { 
		fld.value = ''; 
	} else {
		if (fld.value == '') { 
			fld.value = 'your email address';
		}
	}
}

function checkContactForm() 
{
	if (!isValidEmail(document.getElementById("email").value)) {
		alert("Invalid email. Please, check your input.");
		return false;
	}
	
	return true;
}

function isValidEmail(str)
{
	var regexp = /^[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-_]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-_]*[a-z0-9])?$/gi;
	return regexp.test(str);
}