The Firefox "Page Info" window gives you details about the page you're on. You can also use it to change permissions for the website.
A Refresh can fix many issues by restoring Firefox to its default state while saving essential information like bookmarks and passwords.
The Options/Preferences panels give you access to Firefox settings. This article describes what types of settings are available in each panel.
Firefox warns you when a login form is not secure and your information could be stolen.