One doesn't "configure certain settings on a webpage" and doing any kind of config with the contents of textboxes in a form on an html page (even if https) verges on suicidal.

Please clarify.

• WHAT are you trying to configure:
  • the browser?
  • some other program?
    or
    
  • the rendering of the webpage content? (In that case, knowledge of your markup langugage - html? - and perhaps CSS is what you need)
• If you merely need to prepopulate textboxes (and that's readily done if you know your markup), why are you not creating the page -- prepopulated content, included -- with the "app" ("CGI script")?
    and (though your problem statement appears to rule this out)
• if you're merely providing info so a user can apply it, a "form" in the sense of html is not the way to do it: use a list or table or even simple paragraphs.

I'll explain the problem in detail. There's a form (say abc.html) where you configure certain settings (fill in text boxes and click on submit). Clicking on Submit saves the values so that the next time you open abc.html you can see the values entered earlier. Now these settings are the same every time you configure it. I want to save these settings in a text file, read these and then using a script populate the fields in the form abc.html. That way I don't have to type in the settings every time. I can just open my app, enter abc.html in the appropriate box and the click of a button will do the settings for me. Hope it's clear now.

Much clearer.

So, some more questions:

• "Clicking on Submit saves the values"
  How? Where? (eg, a cookie, a file (on server? in the browser's machine? Are both the same box?) (How you get them back depends on this...and please tell me you're not saving the values to --ie, rewriting-- abc.html.)
• "I don't have to type"
  Should we take "I" literally, as in never anyone other than you personally or is that (misleading) shorthand for "any one of some number > 1 users"?
• "I can just open my app"
  Which is? Another web page; something you execute in a terminal? A GUI ap, depending on X-windows, W32 or ???
  and where will that be located: on a remote server or locally?

I may be way off base on this, but it sounds -- at this point -- as if you have a system design problem, as in "too complex." Think "going all around Robin Hood's barn!" Why not just write your config options into the ap itself or create config script for the ap?

Update: Added concern about rewriting and Robin Hood.