how to get the previous url when user click on back button in browser

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ASP.NET

Javascript

jQuery

I am using asp.net. I have a main menu. what I have done is,in the Home/About page,when user click on the menu I replacing the About page content by selected page content selected in the menu.

$("#content").html(iframeof selected menu url);

here,content is in About page . My problem is when I click on browser back button,It is redirecting to the log in page,not redirecting to the previous selected page.

how can I display the previous page when user click on the browser back button.