define_tag(
	'gravatar',
	-req='email',
	-opt='rating',
	-opt='default',
	-opt='size', -type='integer',
	-priority='replace',
	-encodenone,
	-description='Retrieves the Gravatar for the given email address.'
);
	fail_if(
		!valid_email(#email),
		-1, 'Email address supplied is not valid.'
	);

	fail_if(
		local_defined('rating') && (:'G','PG','R','X') !>> #rating,
		-1, 'Rating must be one of G, PG, R, or X.'
	);
	
	fail_if(
		local_defined('size') && (#size < 1 || #size > 80),
		-1, 'Size must be between 1 and 80.'
	);
	
	fail_if(
		local_defined('default') && !valid_url(#default),
		-1, 'Default must be a complete, valid URL.'
	);

	local('hash') = encrypt_md5(#email);
	local('url') = 'http://www.gravatar.com/avatar.php?gravatar_id=' + #hash;
	local_defined('rating') ? #url += '&rating=' + #rating;
	local_defined('size') ? #url += '&size=' + #size;
	local_defined('default') ? #url += '&default=' + encode_stricturl(#default);
	return(#url);		
/define_tag;