I need to know if there is a user name and password associated with accessing a certain website.

I'm not sure if at one time there was a username and password given so that I automatically could access a site. The site is the home page for my department on the intranet of the company I work for, and they've activated a new vpn. If I use Safari, after activating the vpn opening Safari, it asks me for a user name and password for some proxy server and from there on out I can navegate the external web or the company intranet. Using Firefox, I do not get prompted for a user name and password but I cannot access my homepage yahoo.com or any public website; I can, however access my company's intranet. The IT guy says there must be some user name & pw to access the site that I've previously asked Firefox to memorize but which I can't see. I don't think so but I can't figure out where to find the list of sites that Firefox has memorized passwords for.