Webrowser Autofill Page With Frames?

I'm tryin to auto-submit username and password in a web page, although i have done it many times came across a website that common solution doesn't seems to work.This is the url By clicking the top right text "Χρήστες" i'm getting the submit page but the url remains the same despite the fact that the text's address is [URL]cfm?Inspecting the element with firebug giving me the following

<script language="JavaScript">
var check=(document.layers&&window.innerWidth==0)?0:1;
if((((top.location.href!='https://www.taxisnet.gr/web/') && (top.location.href!='https://www.taxisnet.gr/web/default1.html') &&

[code].....

It seems that i must work with frames tried many things and can't get a handle of the boxes. Innerhtml won't work, elementID or name doesn't work although i have both

<input size="16" name="username" class="textbox">