Google has long waged a war on the insecure HTTP protocol in Chrome, instead favoring HTTPS, and now it seems that Mozilla is joining in by bringing the same functionality found in version 56 of Chrome over to version 51 of Firefox. Mozilla has been waging their own war on HTTP, with word of deprecating the insecure web standard going back as far as April of 2015, so when Google's Chrome browser beat Mozilla and their flagship Firefox browser to the punch, it wasn't a huge logical leap to assume that they would be implementing their own way of warning users about insecure HTTP connections soon. Now, both browsers share the functionality.
In Chrome, an insecure page will generate a broken lock icon and a few other indicators in the Omnibox, letting a user know that it's probably a bad idea to transmit anything sensitive on that page unless they implicitly trust the page's owner. When a user tries to submit anything sensitive over that connection, such as a password or credit card number, Chrome pops up a warning. In Firefox, things are much the same. A lock icon with a strike-through will appear in the address bar when visiting a site that's not properly secured, and clicking on the round "i" icon to get more information will tell you if you have granted the site in question any permissions, and give you some more details about its insecure status.
In both cases, the goal is essentially to push web developers to embrace the more secure standard by increasing user awareness of poor security practices, which will in turn make those users think twice before using the page in question for any kind of sensitive or secure operation. This will end up decreasing traffic, even if only a little, and may just be the push that the web needs to start phasing out HTTP altogether. Chrome version 56 is out in the stable channel for desktop users right now, and should be rolling out over the next few weeks. Firefox version 51 has been officially out since January 24, and is also rolling out to desktop users, though a download link is available for those who don't want to wait for the update to make its way to them.