If you use Safari as your default browser and use Tweetbot for Mac, you may have had an issue on OS X El Capitan where links wouldn't load the first time, they would just appear as "loading."
You need to hit
⌘+R until, eventually, Safari says that it couldn't load the link and hitting
⌘+R one more time finally loads what you were trying to see. A full minute later.
To fix this, open Terminal.app and paste the following:
defaults write com.tapbots.TweetbotMac OpenURLsDirectly YES
Press enter, and voilà.