Xrm.Page.data return null

Hi,

In crm online 2015 I open a webResource:
Xrm.Utility.openWebResource("new_addGoalsObjectivesMeasures",null,1500,1200);
new_addGoalsObjectivesMeasures is html webResource.
I want to get the guide of the record which I came from.
I write: Xrm.Page.data.entity.getId();
But Xrm.Page.data returns null.
Also when I write: parent.Xrm.Page.data.entity.getId(); it is null.
What do I am doing wrong?
Thanks!