It's crazy that latest browsers are hiding http protocol from the location bar. As a developer sometimes i need to just add 's' on http:// to test SSL as https:// but i have to type everything to test. Also when I just want to copy the domain name it copies with http protocol. But i am not that fan of this. I prefer to view http:// on the location bar.
After some google search found this tips that did the trick.
Steps to Show/Enable http:// in Firefox URL location bar.
1. Type 'about:config' in the address bar and press enter proceed by agreeing to the warning.
2. Double-click on browser.urlbar.trimURLs preference to turn it's value to false.
Now type any website URL in the browser, http:// will be shown greyed out i.e. not highlighted. But if you don't like it greyed out then you can set 'browser.urlbar.formatting.enabled' preference to false after the above mentioned steps to remove the highlighting.