User is not prompted to save changes when closing the form.

Hi,

User is not prompted to save changes when closing the form. 
	
After modifying or deleting the field when closing the form without showing message "Do you want to save the changes" form is closing.
	
Iam using forms 10g. can anyone please tell what are the triggers i need to check for and the reason for not getting the message?
	
	
Thanks.