I'm trying to display an image that is stored as a Document. Starting with the most basic example, I am using the following:
 

<apex:page standardcontroller="Document">

  <apex:outputField value="{!Document.name}"/>
  <apex:image id="theImage" value="!Document.Logo.jpg" width="100" height="100"/>

</apex:page>

passing the ID of the document in through the URL. It's Name displays OK, but the image does not, just showing as a 'dummy' 100x100 blank square. What syntax do I need to use? Or do I need a different approach some how?
Note, I do not want to use a Static Resource.
Thanks

I'm also having trouble with this challenge. With the logic below I get the error "The validation rule failed to enforce the business logic". But when I leave out the NOT (ISBLANK( checks for MailingPostalCode or Account.ShippingPostalCode I get a worse error "FIELD_CUSTOM_VALIDATION_EXCEPTION". Here's what my rule looks like:

Hello All,
I have completed this challenge.

1-For this first you need to create a helper formula field(type-percent) 
Percent Completed :
(DATEVALUE( CreatedDate ) - CloseDate )/100

2- Then you need to create the actual formula field (type- text) by using the helper formula field.
Opportunity Progress :

IF( Percent_Completed__c <=25,"Early", 
IF(Percent_Completed__c <=75,"Middle", 
"Late"))

Thanks,
Nida