Guild Wars 2

Per topic, this message gives me some concern. Why do the pages on this forum want to install anything on my end?

They don’t and this should be alarming for you. A service handler is usually needed for non-standard protocols, e.g. Skype does that so that you can use skype://xyz links on a website. All pages under guildwars2.com use standard http and https protocols so that you won’t need to install anything. Ever. If so, go and check for the source of this, also a more detailed description (screenshot if possible) and your software configuration (OS/Browser) could be helpful in order to help you get rid of this.