Last March Twitter implemented new functionality that allowed users to increase their security by allowing them to browse Twitter.com via a HTTPS (HTTP Secure) server.
HTTPS provides encrypted communication and secure identification on a web server, and is most commonly used for financial transactions. HTTPS for Twitter (and also Facebook, which activated HTTP Secure browsing in January 2011) offers greater protection when accessing the network over unsecured WiFI connections.
Now, in an effort to further improve user safety, Twitter has made HTTPS the default setting for all profiles.
Websites that are HTTPS secure display a small lock in the address bar (which sometimes turns green, depending on your browser). Now, when you use Twitter.com, every page you visit will use HTTPS.
You can opt out of HTTPS on Twitter.com by unticking the box in your Settings.
Why would you want to opt out? If you always use Twitter.com on a secure network, HTTP will speed up your experience, as the HTTP Secure server does slow things down somewhere. If, however, you’re always using Twitter out and about, it’s highly recommended that you activate the HTTPS setting and leave it that way permanently.