If I understand correctly, you have 2 problems:
- you need to redirect from your aspx page to a local html page
- you need to redirect from a local html page back to your server page
To solve nr 1 you will need to know the absolute location path to the html page on the client machine (ie. C:\SomePath\LocalFile.html) then do a link there:
<a href="file:///C:\SomePath\LocalFile.html">
And no, it's not possible to access local files from javascript.
At most you can ASK the user to point to the local file (ie.via a file upload input) then intercept that event and use the path to that file.
window.location.href=document.getElementById('fileInput').value;
but even that is riddled with problems as it will not work in some browsers,etc.
To solve nr2 you will probably need to add some javascript (which by default is turned off for local html files!!) and use "history.previous" to detect the path to your public aspx page. Something in the order of :
window.location.href= history.previous.replace("myfirstpage.aspx","redirectedpage.aspx");
which will send someone that came to the current page from ,say, "http://www.publicserver.com/myfirstpage.aspx", will be redirected to "http://www.publicserver.com/redirectedpage.aspx",