Unable to getId of lead in Html external page?

Hi,

I have created one dropdown when i select the value in my dropdown it will trigger one script , this js function will open html popup page.So, i want to put my crm lead form value in html page input.Here i am using OData to do this task.But when i trigger the OData script from html page it shows null on the 

GUID = parent.Xrm.Page.data.entity.getId(); 

If i use this method on my js and trigger it then it shows guid.But when i use it from the html popup page it doesn't work.

Please help.