when pop up came up, parent page should be cover or invisible

HI,
I hipe this is right place to ask.


I have parent page and child page.


when i click hyperlink from parent page, child page will pop up . At that time I want my parent page to cover with something or invisible.


bz in the child page, i let user to answer question and answer. when they answering question, i wont let user to click hyper link again from my parent page. how would i disable my parent page.


thanks,

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