How to prevent/restrict changes to parent window contents when the child windows are open in ASP Application. How to handle the same if the child windows contains frames and open 2 or more ASPs within. Also this child may further become as a parent to open new child. Please advice.

IF your referring to frames then you need
to "Target" your form or link to the name of the child.

<Form Name=MyForm Action=NewASP.asp
Method=Post Target=ChildName>

OR

<a Href=NewASP.asp Target=ChildName>