This is a default feature of browsers. I believe it is intended to help with phishing attacks. For example, if someone sent a link to someone who is not very tech savvy that showed a link to "Login to correct your information", and you hovered over the link and it showed "http://fakeAttemptToStealYourInfo.hacker/sdlkjdflksd", it would hopefully give them a chance question the link before clicking.