title: cloudformation validation returns: Invalid template resource property
body: <p>Consider this part of a cloud formation template:</p>
  
  <pre><code># VPC
      myVPC:
        Type: "AWS::EC2::VPC"
        Properties:
          CidrBlock: 10.99.99.0/24
  
  # Security group
  
      http_sec_group:
        Type: "AWS::EC2::SecurityGroup"
        Properties: 
          GroupName: http_in
          GroupDescription: "Allow http traffic inbound"
          VpcId: !Ref myVPC
          SecurityGroupIngress:
            - ToPort: 80
              IpProtocol: tcp
  </code></pre>
  
  <p>Validating it returns this error:</p>
  
  <p>An error occurred (ValidationError) when calling the ValidateTemplate operation: Invalid template resource property 'myVPC'</p>
  
  <p>The syntax looks correct, but why does the reference return an error?</p>