And "hi" back, Yagna
. Welcome to the Monastery.
But I'm confused. You say "I want the user to be logged into the main webpage."
Do you mean "logged into the default page (perhaps index.html -- ie, in some vernaculars, what's called the "landing"page) for the visitor initially arriving at your site, or do you mean that a successful login puts the user on a page whereon s/he can interact with the "two page application?"
My personal preference is to have the login script redirect to the ap if the uname/pw passes your tests... and, otherwise, to have it call a second CGI script which will throw up a new page which says 'That username doesn't match that password" or similar and provides a link (emphasis, LINK; NOT a redirect>) to the default (index.html or whatever).
I'm not going to bother to offer a detailed (and perhaps even rational) explanation of that preference; it's not something I've detailed -- in my own mind; let alone on paper -- to the degree needed to make it readable and defensible (which it may or may not be) :( .