function GetId(id) {
	if(document.getElementById) // standardised method first
		return document.getElementById(id);
	else if(document.all)
		return document.all[id];
	else if(document.layers)
		return document.layers[id];
	else
		return null;
}

function CheckForm(){
	var email = GetId('email').value;
	var name = GetId('name').value;
	var message = GetId('message').value;

	var err = new Object();
	var err;
	if(name == '')
		err['name'] = 'You must fill your name';
	
	if(email == '')
		err['email'] = 'You must fill your email address';
	else {
		var email_reg = /^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,4})$/;
		if(email_reg.test(email) == false)
			err['email'] = 'You email address is invalid';
	}
	
	if(message == '')
		err['message'] = 'You must enter a message';
	
	var i = 0;
		for ( key in err ) {
			i++
		}	
	if(i != 0){
		GetId('alert').className = 'error';
		var res = 'The following errors were found while verifying form fields :\n<ul>';
		for ( key in err ) {
			res += '<li>'+err[key]+'</li>\n';
		}
		res += '<ul>';
		GetId('alert').innerHTML = res
	}
	else
		GetId('contact_form').submit();
}