why am I having Xrm.Page.Data always equals null in javascript in CRM Web resource?

I am trying to use a web resource in Dynamics CRM 2011. When using Xrm.Page.Data, I always have Data as null.

What can be missing o开发者_Go百科r wrong here?

1. Make sure you're waiting for the onload event to execute your script. data will be null before this (detail forms).
2. I'm not sure it is available at all in grid views / other ribbon contexts.
3. It is Xrm.Page.data (data is all lower case).