var error_colour = '#FFAAAA';
var ok_colour = '#FFFFFF';

function check_fields()
{	
	var result = true;
	
	for ( var i = 0; i < arguments.length; i ++ )
	{
		var field_ok = true;
		var field_name = arguments[i][0];
		var field = document.getElementById( field_name );
		var field_error_message = document.getElementById( field_name + '_error_message' );
		var validation_criterion = parseInt( arguments[i][1] );
		
		if ( validation_criterion == 0 ) // is *anything* entered?
		{
			if ( field.value == '' ) field_ok = false;
		}
		else if ( validation_criterion == 1 ) // is this an e-mail address?
		{
			at_position = field.value.indexOf( '@' );
			dot_position = field.value.indexOf( '.', ( at_position + 1 ) );
			
			if ( at_position == -1 || dot_position == -1 ) field_ok = false;
		}
		
		if ( field_ok == false )
		{
			result = false;
			field.style['background'] = error_colour;
			field_error_message.style['display'] = 'block';
		}
		else
		{
			field.style['background'] = ok_colour;
			field_error_message.style['display'] = 'none';
		}
	}
	
	return result;
}