Simply put, Panic Mode is an extension for Chrome and soon for Firefox, which allows you stay secure online. When you turn it on, all http trafic from your browser will be forced to use SSL guarantying your privacy on untrusted networks such as those used by Hotels and Public WiFi access points at train stations and airports.
Panic Mode is designed to force SSL and not to be too clever or assuming about things. In other words, if the site you are trying to reach does not support SSL in some way, it will break and that breakage will be plainly obvious to you. This is actually a good thing. Overtime you will learn which sites are bad and which are good. Panic Mode is really designed to fix your privacy concerns by breaking websites for you.